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Three-component coupling of CO2, propargyl alcohols, and amines: An environmentally benign access to cyclic and acyclic carbamates (A Review)
Journal of CO₂ Utilization 21 (2017) 108–118
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Review Article
Three-component coupling of CO2, propargyl alcohols, and amines: An environmentally benign access to cyclic and acyclic carbamates (A Review)
MARK
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Sattar Arshadia, , Esmail Vessallya, Akram Hosseinianb, Somayeh Soleimani-amiric, Ladan Edjlalid a
Departmentof Chemistry, Payame Noor University, Tehran, Iran Department of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran c Department of Chemistry, Karaj Branch, Islamic Azad University, Karaj, Iran d Department of Chemistry, Tabriz Branch, Islamic Azad University, Tabriz, Iran b
A R T I C L E I N F O
A B S T R A C T
Keywords: CO2 Carbamates 2-Oxazolidinones β-Oxoalkyl carbamates Three-component reactions Carbonates Catalyst
Carbamates are key intermediates in the synthesis of a variety of pharmaceutically important compounds and fine chemicals. Moreover, they have been widely applied as chiral auxiliaries in asymmetric transformations. Consequently, much efforts have been devoted to the design and synthesis of these compounds. Synthesis of titled compounds utilizing carbon dioxide as a feedstock is more attractive in comparison to other processes, because CO2 is an abundant, cheap, green, nontoxic, non-flammable, and renewable C1 resource. In this mini review, we highlight the advances in synthesis of cyclic and acyclic carbamates through three-component coupling of CO2, amines and propargyl alcohols from 1987 to 2017.
1. Introduction Global warming is caused by the extensive emission of carbon dioxide (approximately 38000 million tons per year), and therefore, many efforts have been devoted to developing versatile processes to its capture and utilization [1]. Conversely, CO2 can be used as a safe, nontoxic, and inexpensive building block to produce various valuable organic compounds, such as carboxylic acids, esters, alcohols, amides, aldehydes, carbonates, and carbamates [2]. Needless to say, access to organic compounds by multicomponent routes is particularly attractive in terms of synthetic efficiency, and also from the environmental point of view [3]. 2-oxazolidinones (five-membered cyclic carbamates) are one of the most important skeletons which not only show interesting biological and therapeutic activities (Scheme 1) [4], but also used as a building block in organic synthesis [5]. In particular, they have been widely applied as chiral auxiliaries in asymmetric syntheses [6]. Some of the most important methodologies for the preparation of 2-oxazolidione derivatives from CO2 are summarized as follows: (1) chemical fixation of CO2 to substituted aziridines [7]; (2) chemical fixation of CO2 to 2amino alcohols [7]; (3) chemical fixation of CO2 to N-propargylamines [8]; and (4) cycloadditon reaction of propargylic alcohols with primary amines and CO2. Compared to the other methods, cycloaddition reactions of carbon dioxide with propargylic alcohols and amines has remained largely underdeveloped. In continuation of our works on
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synthesis of nitrogen-containing heterocycles from propargylic compounds [9], in the first section of this review, we will highlight the most important developments on synthesis of 2-oxazolidinones through three-component coupling of propargylic alcohols, CO2, and primary amines (Fig. 1, path a), which will be helpful in the development of improved methods for the synthesis of complex and biologically important cyclic carbamates. Acyclic carbamates are widely encountered in the structure of pharmaceuticals [10], and pesticides [11] (Scheme 2). The classical method for the synthesis of carbamates generally involves the use of highly toxic phosgene or isocyanate derivatives as starting material which may cause serious environmental pollution and safety problems [12]. Over the past three decades, CO2 has emerged as an alternative to phosgene and isocyanates in carbamate synthesis. Synthesis of β-oxoalkyl carbamates via three-component coupling of CO2, secondary amines and propargyl alcohols have undergone an explosive growth in recent years (Fig. 1, path b). This new page of carbamate synthesis offers several advantages, such as: (1) nontoxic by-products; (2) high atom economy; (3) ease of handling; (4) cheap and simple starting materials and many more. To the best of our knowledge, a comprehensive review has not appeared on the synthesis of β-oxoalkyl carbamates through three-component reaction of propargylic alcohols, amines, and CO2 in literature so far. The second section of this review will discuss on the synthesis of β-oxoalkyl carbamate derivatives via three-component reaction of propargylic alcohols, secondary amines,
Corresponding author. E-mail addresses: [email protected], [email protected] (S. Arshadi).
http://dx.doi.org/10.1016/j.jcou.2017.07.008 Received 11 May 2017; Received in revised form 13 June 2017; Accepted 5 July 2017 Available online 11 July 2017 2212-9820/ © 2017 Elsevier Ltd. All rights reserved.
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Scheme 1. Selected examples of drugs containing 2-oxazolidione core.
oxazolidinones 10 (Scheme 4). According to the author proposed mechanism this reaction proceeds via the initial formation of an α-alkylene cyclic carbonate B from the starting propargylic alcohol 7 and CO2 through intermediate A. Next, a nucleophilic addition of primary amine 8 to intermediate B occurs to produce 2-oxoalkylcarbamate C, which then undergoes an intramolecular cyclization to produce 4-hydroxy cyclic carbamate D. Finally, a regioselective dehydration takes place to give the expected products 9 and 10 (Scheme 5) [16]. Inspired by these works, the group of J. Zhao developed an analogous one-pot access to 5methylene-2-oxazolidinones 13 by the three-component reaction of tertiary propargylic alcohols 11, primary amines 12, and CO2 at atmospheric pressure under solvent free-conditions using CuCl as catalyst (Scheme 6) [17]. The yields are somewhat lower than those reported by Jiang, but the products could be smoothly achieved under mild conditions. In 2009, Jiang and Zhao reported that the commercially available AgOAc was highly effective catalyst for the cycloaddition reactions of carbon dioxide with internal propargylic alcohols 14 and primary amines 15. Other silver catalysts, such as AgBF4 and Ag2CO3 were also found to promote this three-component reaction; however, in lower yields. The reaction was carried out under supercritical conditions at 120 °C and provided corresponding 2-oxazolidinones 16 in good to excellent yields (Scheme 7). The reaction is noteworthy in that both alkyl and aryl substituted internal propargylic alcohols is tolerated. It should be mentioned that the substitution pattern of starting alcohols had no effect on the regioselectivity of reaction. Thus, it is found that the primary, secondary and tertiary alcohols 14 underwent the reaction smoothly, furnishing the corresponding 2-oxazolidinones 16, without any of oxazolones [18]. Recently W. Li and L. He along with their co-workers were able to demonstrate that a range of 5-methylene-2-oxazolidinones 19 could be obtained from the three-component reaction of tertiary propargylic alcohols 17, primary amines 18 and CO2 at 0.5 MPa pressure under solvent-free conditions employing Ag2WO4 as catalyst and Ph3P as additive. The corresponding 2-oxazolidinones 19 were obtained in 83–95% yields (Scheme 8a). The authors found that this bifunctional
and CO2. Mechanistic aspects of the reactions are considered and discussed in detail. 2. Cyclic carbamates 2.1. Metal catalyzed reactions Chemical fixation of carbon dioxide by metal-catalysts has attracted a lot of attention because of these catalysts allow for rapid transformations under mild conditions with low loading. These flexible catalysts can also be easily separated and reused several times without obvious loss in the catalytic activity and selectivity [13]. In 1987, Sasaki et al. published the first example on the synthesis of cyclic carbamates through metal catalyzed cycloadditon reaction of propargylic alcohols with primary amines and CO2. They showed that the reaction of propargylic alcohols 1 with n-propylamine 2 in the presence of Ru3(CO)12 as catalyst under carbon dioxide atmosphere can produce the corresponding oxazolones 3 in low to moderate yields (Scheme 3a). The results demonstrated that secondary propargylic alcohol 1b was more reactive than primary propargylic alcohol 1a [14]. Eighteen years later, Deng and co-workers were able to extended this chemistry to the synthesis of functionalized 2-oxazolidinones. They found that treatment of tertiary propargylic alcohols 4 with primary amines 5 and CO2 in the presence of cheap and easily accessible CuI as catalyst in [BMIm]BF4 medium produced the corresponding 4-methylene-2-oxazolidinones 6 in high to excellent yields (Scheme 3b). In this study, the authors found some limitations in their methodology when they attempted to react primary and secondary propargylic alcohols. In these cases, they observed no formation of 2-oxazolidinone product. In addition, aniline also failed to form the desired product [15]. Shortly afterwards, Jing, Zhao, and Wang reinvestigated this reaction using CuI as catalyst under supercritical conditions. The author found that the substitution pattern on propargylic alcohols 7 had a fundamental influence on the regioselectivity of reaction. Thus, reaction of primary and secondary propargylic alcohols gave oxazolones 9, whereas reaction of tertiary propargylic alcohols lead to 5-methylene-2-
Fig. 1. Schematic representation of the three-component coupling of CO2, propargyl alcohols, and amines.
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Scheme 2. Chemical structure of some of the marketed drugs and pesticides containing carbamate moiety.
alkylidene cyclic carbonate, azolidinones (Scheme 10) [20].
silver tungstate catalyst simultaneously activate both the propargylic substrate and CO2 which cooperative catalytic mechanism by the silver cation and the tungstate anion (Scheme 8b). It is noted that under this reaction conditions, internal propargylic alcohols failed to form the desired product and secondary alcohols gave the oxazolone derivatives [19]. Very recently, the same research team presented one of the most striking examples of the synthesis of 2-oxazolidinone derivatives 22 via silver-catalyzed three-component cascade reaction of terminal propargylic alcohols 20, 2-aminoethanols 21, and CO2 (Scheme 9). In their optimization study, the authors found that the use of 5 mol% of Ag2CO3 and 10 mol% of Xantphos in chloroform gave the best results. The presence of additive was critical for the success of this reaction, no reaction occurred in the absence of the additive. Under optimized conditions the reaction tolerated a variety of functional groups, such as chloro, methoxy, nitro, and hydroxy functionalities and gave final products in moderate to excellent yields. According to the author proposed mechanism, the reaction proceeds through formation of α-
β-oxopropylcarbamate,
and
2-ox-
2.2. Organocatalyzed reactions Over the last few decades, organocatalysts (organic catalysts) has attracted much attention from both academia and industry, and emerged as one of the hot topics in advanced organic chemistry. These catalysts are often robust, affordable, non-toxic, and insensitive to the air and moisture, and thus are easy to handle. A remarkable number of organocatalysts and processes, such as one-pot, tandem, cascade or multicomponent reactions, have been reported to date [21]. In 1990, the group of Fournier demonstrated for the first time the usefulness of organocatalysts for the cycloadditon reaction of propargylic alcohols with primary amines and CO2. Thus, in the presence of tributylphosphine (Bu3P) as catalyst at 110–140 °C, three component coupling reaction of CO2, 2-methylbut-3-yn-2-ol 24 and primary amines 25 furnished corresponding 5,5-dimethyl-4-methylene-2-oxazolidinones Scheme 3. (a) Ru-catalyzed three-component reaction of propargylic alcohols 1, primary amines 2, and CO2 developed by Sasaki; (b) Synthesis of 4-methylene-2-oxazolidinones 6 through Cu(I)-catalyzed reaction of propargylic alcohols 4, primary amines 5 and CO2.
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Scheme 4. Cu(I)-catalyzed cycloaddition reaction of carbon dioxide with propargylic alcohols 7 and amines 8 to produce oxazolones 9 and 2-oxazolidinones 10.
Scheme 5. Mechanistic proposal for the reaction in Scheme 4.
Scheme 6. Cu(I)-catalyzed three-component reaction of tertiary propargylic alcohols 11, primary amines 12, and CO2.
Scheme 7. Silver-catalyzed cycloaddition reactions of carbon dioxide with internal propargylic alcohols 14 and primary amines 15.
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Scheme 8. (a) Ag2WO4-catalyzed three-component reaction of propargylic alcohols 17, primary amines 18 and CO2; (b) Cooperative catalytic mechanism by the silver cation and the tungstate anion.
Scheme 9. Synthesis of 2-oxazolidinones 22 through Ag-catalyzed three-component reaction of propargylic alcohols 20, CO2, and 2-aminoethanols 21.
Scheme 10. Mechanistic proposal for the reaction in Scheme 9.
26 in moderate to good yields (Scheme 11) [22]. The main advantage of this protocol compared to the metal catalyzed processes is that aromatic amines can be subjected to couplings to give N-aryl 2-oxazolidinone derivatives. Along this line, Costa and co-workers reported the cycloaddition reactions of supercritical carbon dioxide with tertiary propargylic alcohols 27 and primary amines 28 by using bicyclic guanidine catalysts. The reaction tolerates both alkyl and arylamines and gave final product 29 in moderate to good yields (Table 1). The results revealed that the alkylamines are extremely reactive than arylamines. According to
mechanistic studies, it proceeds through the formation of a cyclic carbonate C from the starting tertiary propargylic alcohol 27 and CO2 through intermediates A and B, following the nucleophilic attack of primary amine 28 to the carbonyl group of the intermediate C to give the acyclic carbamate D, which then undergoes a cyclization by intramolecular attack of the amino group to the ketonic carbonyl to produce intermediate E. The last step of the transformation involves the dehydration of E to the final 2-oxazolidinone 29 (Scheme 12) [23]. In a closely related investigation, Liu and Hua disclosed that 2,2′,2”-terpyridine could efficiently catalyze cycloaddition reaction of CO2 with 112
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Scheme 11. Bu3P-catalyzed coupling of 2-methylbut-3-yn-2-ol 24, primary amines 25, and CO2 reported by Fournier.
Table 1 Guanidine-catalyzed synthesis of 2-oxazolidinones 29 from terminal propargylic alcohols 27, primary amines 28, and CO2.
Entry 1 2 3 4 5 6 7 8 9 10 11 12 13
R1 Me Me Me Me Me Me Me Me Me Me -(CH2)5-(CH2)5-(CH2)5-
R2 Me Me Me Me Me Me Me Ph Ph Ph
R3NH2 n-BuNH2 n-BuNH2 butan-2-amine t-BuNH2 allylNH2 BzNH2 PhNH2 n-BuNH2 n-BuNH2 PhNH2 n-BuNH2 n-BuNH2 PhNH2
Catalyst MTBD TBD MTBD MTBD MTBD MTBD MTBD MTBD TBD MTBD MTBD TBD MTBD
Yield (%) 78 78 72 – 72 67 38 72 21 15 69 65 33
Scheme 12. Mechanism proposed to explain the synthesis of substituted 2-oxazolidinones 29 developed by Costa.
Scheme 13. 2,2',2”-terpyridine catalyzed reaction of carbon dioxide with propargylic alcohols 30 and primary amines 31.
2.3. Ionic liquid catalyzed reactions
terminal propargylic alcohols and amines. Under optimized conditions (2,2′,2”-terpyridine, 5 mol%, solvent-free, 140 °C) various propargylic alcohols, including secondary and tertiary alcohols, react to give good yields of the corresponding products (Scheme 13). However, internal propargylic alcohols failed to participate in this reaction [24].
Ionic liquids are salt-like materials that are liquid at unusually low temperatures. They are nonflammable, non-volatile and recyclable and therefore have been widely applied in multitude of areas such as 113
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Scheme 14. Synthesis of 4-methylene-2-oxazolidinones 35 via treatment of tertiary propargylic amines 33 with cyclohexanamine 34 under CO2 atmosphere in ionic liquid.
Scheme 15. (a) Ru-catalyzed synthesis of carbamates 38 developed by Bruncau; (b) Ru3(CO)12mediated synthesis of carbamates 41 reported by Sasaki.
3. Acyclic carbamates 3.1. Metal catalyzed reactions Metal-catalyzed three-component reaction of propargylic alcohols, carbon dioxide, and secondary amines provide powerful and flexible protocols for preparation of acyclic carbamates. These reactions have been abundantly used for synthesis of special β-oxoalkyl carbamate derivatives. One of the earliest reports of the applicability of these reactions, has been reported by Bruncau and Dixncuf in 1987, when terminal propargyl alcohols 36, secondary amines 37, and CO2 underwent a three-component coupling reaction in the presence of [RuCl2(norbornadiene)]n as catalyst in acetonitrile to form carbamate 38 (Scheme 15a) [27]. The desired products were isolated in low to moderate yields. At the same time, Sasaki reported independently a similar strategy for the preparation of β-oxoalkyl carbamates 41 from corresponding propargylic alcohols 39 and amines 40 by using only 1 mol% of Ru3(CO)12 as catalyst in MeCN (Scheme 15b). However, this reaction system also gave low to moderate yields of the desired products [14]. Inspired by these works, the group of Shi described that lanthanide chlorides (Scheme 16a) [28] and iron complexes (Scheme 16b) [29] were good catalysts for this reaction. Just like previous works, the desired products were isolated in low to moderate yields.
Scheme 16. Lanthanide and iron complexes as catalysts for the synthesis of acyclic carbamates from corresponding propargylic alcohols, amines, and CO2.
organic synthesis, catalysis, solar cell, fuel cells, and many more. However, they suffer from some serious drawbacks such as high cost of preparation, and tedious separation and recovery from reaction medium [25]. The reported examples for synthesis of 2-oxazolidinones through ionic liquid catalyzed cycloaddition reactions of carbon dioxide with propargylic alcohols and amines are scarce and to the best of our awareness there is only one example on this chemistry. In 2005, Deng and co-workers showed that the treatment of α,α-disubstituted propargyl alcohols 33 with cyclohexanamine 34 in ionic liquid [DMIm] [BF4] under carbon dioxide atmosphere for 10 h afforded corresponding 4-methylene-2-oxazolidinone derivatives 35 in moderate to high yields (Scheme 14). It should be mentioned that the ionic liquid playing a dual role in this reaction; the solvent and the catalyst [26].
Scheme 17. Ag/DBU-catalyzed synthesis of carbamates 41 reported by Jiang.
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Scheme 18. Mechanistic proposal for the reaction in Scheme 17. Scheme 19. Bifunctional silver(I) complexcatalyzed reaction of terminal propargylic alcohols 45, secondary amines 46, and CO2.
Scheme 20. 1H NMR (a, b) and 13C NMR (c–f) investigation. (a, b) 2-methyl-4-phenylbut-3-yn-2-ol (8.0 mg), Ag2CO3 (2.8 mg) and Ph3P (10.5 mg) ([D6]DMSO 0.6 mL). (c,d) 2methylbut-3-yn-2-ol (20.2 mg), AgNO3 (40.8 mg) (CDCl3 0.6 mL). (e) [(Ph3P)2Ag]2CO3 (158.6 mg) in 0.6 mL of CDCl3. (f) [(Ph3P)2Ag]2CO3 (158.6 mg) in 0.6 mL of CDCl3 in the presence of 13CO2 (1 bar).
reaction is equally efficient for both the aryl and alkyl substituted propargylic alcohols. Other silver catalysts such as AgNO3, AgBF4, and AgCO3 were also found to promote the reaction; however, in lower yields. It is noted that the sterically hindered diisopropylamine failed to afford the product under this reaction conditions. The mechanism proposed by the authors to explain this reaction involves: (1) the Ag(I)/
Nearly two decades after these works, Qi, Huang, and Jiang applied the AgOAc/DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) system to the cycloadditon reaction of internal propargylic alcohols 42 with secondary amines 43 and CO2. The reaction was run in 1,4-dioxane at 90 °C and in most cases, provided carbamates 44 in good to excellent yields (Scheme 17). The results proved that this Ag(I)-catalyzed 115
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Scheme 21. Ag-catalyzed synthesis of βoxoalkyl carbamates 50 from the reaction between a propargylic alcohols 48 and ammonium carbamate 49.
Scheme 22. Proposed mechanism for formation of 47. Table 2 Guanidine-catalyzed synthesis of carbamates 53 under supercritical conditions.
Entry 1 2 3 4 5 6 7 8 9
R1 Me Me Me Me Me H -(CH2)5-(CH2)5-(CH2)5-
R2 Me Me Me Ph Ph H
R32NH pyrrolidine n-Bu2NH n-Bu2NH pyrrolidine n-Bu2NH pyrrolidine pyrrolidine n-Bu2NH n-Bu2NH
Catalyst MTBD MTBD TBD MTBD MTBD MTBD MTBD MTBD TBD
Yield (%) 79 79 58 78 77 33 81 82 48
gram-scale with little effect on the yield. To elucidate the mechanism of this silver (I) complex-catalyzed CO2 conversion, the authors conducted nuclear magnetic resonance (NMR) spectroscopy investigations (Scheme 20). According to data obtained by 1H and 13C NMR techniques, the authors found that this catalyst simultaneously activate propargylic alcohol and CO2 [31]. Ag2WO4 is another successful Ag(I)based bifunctional catalyst that developed by the same authors for this chemistry [32]. Recently, the same research team reported an alternative strategy for the preparation of β-oxoalkyl carbamates 50 from the reaction between an ammonium carbamate 48 (made using CO2 and secondary
DBU catalyzed incorporation of carbon dioxide into the propargylic alcohol 42 which resulted in Z-alkylidene cyclic carbonate C; (2) nucleophilic addition of amine 43 to intermediate C to give allylcarbamate D; and (3) the tautomerization of D to provide β-oxoalkyl-N,Ndialkyl carbamate 44 (Scheme 18) [30]. In 2014, L. He and co-workers developed a PPh3-promoted, Ag2CO3catalyzed three-component reaction of terminal propargylic alcohols 45, secondary amines 46, and CO2, which allowed for the synthesis of acyclic carbamates 47 in good to excellent yields under very mild conditions (atmospheric pressure of CO2 and 30 °C temperature) (Scheme 19). It is noteworthy that this procedure was applied on the 116
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Scheme 23. Catalyst and solvent-free reaction of propargylic alcohols 54, secondary amines 55, and CO2 to β-oxoalkyl carbamate derivatives 56.
amine) and propargylic alcohols 49 using Ag2O/PPh3 combination as catalytic system in acetonitrile at 60 °C (Scheme 21). Beside good yields, simplicity, and relatively mild reaction conditions were other advantages of this gas-free process. The proposed mechanism for this silver-catalyzed two-component reaction is shown in Scheme 22. It consists of the following key steps: (1) initial formation of propargylic carbonate intermediate A via the reaction of propargylic alcohol 48 with ammonium carbamate 49; (2) interchanging of A with silver(I) catalyst to afford the silver propargylic carbonates B; (3) intramolecular 5-exo-cyclization of intermediate B to give intermediate C via an antiaddition mode; (4) proto-demetallation of intermediate C to give the αalkylidene cyclic carbonate D; and (5) nucleophilic attack of secondary amine to the carbonyl group of the intermediate D followed by tautomerization to produce expected products 50 [33].
derivatives. Notably, the formation of cyclic and acyclic carbamate scaffolds depends on the structure of the amine (primary and secondary) employed. Thus, the coupling reaction of CO2, propargyl alcohols and primiary amines gives corresponding cyclic carbamates while the use of secondary amine led to acyclic carbamate derivatives. These reactions have shown both the environmental and economic advantages. It is noteworthy that most of the conversion of CO2 covered in this review could be promoted by earth abundant metal catalysis such as copper and silver as well as organocatalysts demonstrating the greener feature of the present protocol. We hope that this mini review will encourage synthetic organic chemists to employ this valuable and interesting methodology in synthesis of important carbamate derivatives. References
3.2. Organocatalyzed reactions [1] A. Samanta, A. Zhao, G.K. Shimizu, P. Sarkar, R. Gupta, Post-combustion CO2 capture using solid sorbents: a review, Ind. Eng. Chem. Res. 51 (2012) 1438–1463. [2] (a) D. Yu, S.P. Teong, Y. Zhang, Transition metal complex catalyzed carboxylation reactions with CO2, Coord. Chem. Rev. 293 (2015) 279–291. [3] (a) B.B. Toure, D.G. Hall, Natural product synthesis using multicomponent reaction strategies, Chem. Rev. 109 (2009) 4439–4486. [4] (a) I. Berlin, R. Zimmer, H. Thiede, C. Payan, T. Hergueta, L. Robin, A. Puech, Comparison of the monoamine oxidase inhibiting properties of two reversible and selective monoamine oxidase-A inhibitors moclobemide and toloxatone, and assessment of their effect on psychometric performance in healthy subjects, Br. J. Clin. Pharmacol. 30 (1990) 805–816. [5] (a) S.P. Fearnley, 2-(3H)-Oxazolone-A simple heterocycle with manifold potential, Curr. Org. Chem. 8 (2004) 1289–1337. [6] M.M. Heravi, V. Zadsirjan, Oxazolidinones as chiral auxiliaries in asymmetric aldol reactions applied to total synthesis, Tetrahedron: Asymmetry 24 (2013) 1149–1188. [7] S. Pulla, C.M. Felton, P. Ramidi, Y. Gartia, N. Ali, U.B. Nasini, A. Ghosh, Advancements in oxazolidinone synthesis utilizing carbon dioxide as a C1 source, J. CO2 Util. 2 (2013) 49–57. [8] S. Arshadi, E. Vessally, M. Sobati, A. Hosseinian, A. Bekhradnia, Chemical fixation of CO2 to N-propargylamines: a straightforward route to 2-oxazolidinones, J. CO2 Util. 19 (2017) 120–129. [9] (a) E. Vessally, A new avenue to the synthesis of highly substituted pyrroles: synthesis from N-propargylamines, RSC Adv. 6 (2016) 18619–18631; (b) E. Vessally, A. Hosseinian, L. Edjlali, A. Bekhradnia, M.D. Esrafili, New page to access pyridine derivatives: synthesis from N-propargylamines, RSC Adv. 6 (2016) 71662–71675; (c) E. Vessally, A. Hosseinian, A. Bekhradnia, M.D. Esrafili, New page to access pyrazines and their ring fused analogues: synthesis from N-propargylamines, Curr. Org. Synth. 14 (2017) 557–567; (d) E. Vessally, A. Hosseinian, L. Edjlali, A. Bekhradnia, M.D. Esrafili, New route to 1, 4-oxazepane and 1, 4-diazepane derivatives: synthesis from N-propargylamines, RSC Adv. 6 (2016) 99781–99793; (e) E. Vessally, L. Edjlali, A. Hosseinian, A. Bekhradnia, M.D. Esrafili, Novel routes to quinoline derivatives from N-propargylamines, RSC Adv. 6 (2016) 49730–49746; (f) S. Arshadi, E. Vessally, L. Edjlali, E. Ghorbani-Kalhor, R. HosseinzadehKhanmiri, N-Propargylic β-enaminocarbonyls: powerful and versatile building blocks in organic synthesis, RSC Adv. 7 (2017) 13198–13211; (g) E. Vessally, S. Soleimani-Amiri, A. Hosseinian, L. Edjlali, A. Bekhradnia, New protocols to access imidazoles and their ring fused analogues: synthesis from Npropargylamines, RSC Adv. 7 (2017) 7079–7091; (h) S. Arshadi, E. Vessally, L. Edjlali, R. Hosseinzadeh-Khanmiri, E. GhorbaniKalhor, N-Propargylamines: versatile building blocks in the construction of thiazole
With the objective of designing a greener and eco-friendly procedure to β-oxoalkyl carbamates through reaction of propargylic alcohols with secondary amines and CO2, the group of Costa were able to demonstrate that a range of carbamates 53 could be obtained from the reaction of corresponding terminal propargylic alcohols 51 with aliphatic amines 52 in supercritical carbon dioxide employing bicyclic guanidines such as triazabicyclodecene (TBD) and 7-methyl-triazabicyclodecene (MTBD) as cost-effective and non-toxic catalysts (Table 2). The reaction tolerates both primary and tertiary propargylic alcohols and gave final product in moderate to good yields [23]. 3.3. Catalyst-free reactions In 2007, Qi and Jiang discovered that synthesis of β-oxoalkyl carbamate derivatives through three-component reaction of propargylic alcohols, secondary amines, and CO2, are possible even in the absence of any additional catalyst and organic solvent. Thus, treatment of tertiary terminal propargylic alcohols 54 with secondary amines 55 in the presence of compressed CO2 (14 MPa) at 130 °C furnished corresponding acyclic carbamates 56 in moderate to high yields (Scheme 23). The authors proposed that secondary amines playing a dual role in this reaction; the substrate and the catalyst [34]. 4. Conclusion Development of green processes based on chemical fixation of CO2 has received much attention in synthetic organic chemistry in recent years because CO2 is a safe, cheap, abundant, and renewable C1 resource. As shown in this review, one of the useful transformations in which CO2 has been utilized as a substrate is through the three-component coupling of CO2, amines and propargyl alcohols to provide synthetically and biologically important cyclic and acyclic carbamate 117
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[10] [11] [12]
[13] [14] [15]
[16]
[17]
[18]
[19]
[20]
(2016) 2054–2058. [21] (a) D.W. MacMillan, The advent and development of organocatalysis, Nature 455 (2008) 304–308. [22] J. Fournier, C. Bruneau, P.H. Dixneuf, A simple synthesis of oxazolidinones in one step from carbon dioxide, Tetrahedron Lett. 31 (1990) 1721–1722. [23] N.D. Ca, B. Gabriele, G. Ruffolo, L. Veltri, T. Zanetta, M. Costa, Effective guanidinecatalyzed synthesis of carbonate and carbamate derivatives from propargyl alcohols in supercritical carbon dioxide, Adv. Synth. Catal. 353 (2011) 133–146. [24] H. Liu, R. Hua, Conversion of carbon dioxide into 2-oxazolidinones and 2 (3H)oxazolones catalyzed by 2 2′, 2″-terpyridine, Tetrahedron 72 (2016) 1200–1204. [25] (a) H. Olivier-Bourbigou, L. Magna, D. Morvan, Ionic liquids and catalysis: recent progress from knowledge to applications, Appl. Catal. A 373 (2010) 1–56. [26] Q. Zhang, F. Shi, Y. Gu, J. Yang, Y. Deng, Efficient and eco-friendly process for the synthesis of N-substituted 4-methylene-2-oxazolidinones in ionic liquids, Tetrahedron Lett. 46 (2005) 5907–5911. [27] C. Bruneau, P.H. Dixncuf, Catalytic synthesis of O-β-oxoalkylcarbamates, Tetrahedron Lett. 28 (1987) 2005–2008. [28] S.-C. Shim, J.-O. Baeg, C.-H. Doh, Y.-Z. Youn, T.-J. Kim, Synthesis of carbamates from amine, acetylenic alcohol, and CO2 using lanthanide as catalyst, Bull. Korean Chem. Soc 11 (1990) 467–468. [29] T.-J. Kim, K.-H. Kwon, S.-C. Kwon, J.-O. Baeg, S.-C. Shim, D.-H. Lee, Iron complexes of 1, 1′-bis (diphenylphosphino) ferrocene (BPPF) as efficient catalysts in the synthesis of carbamates. X-ray crystal structure of (BPPF) Fe (CO)3, J. Organomet. Chem. 389 (1990) 205–217. [30] C. Qi, L. Huang, H. Jiang, Efficient synthesis of β-oxoalkyl carbamates from carbon dioxide, internal propargylic alcohols, and secondary amines catalyzed by silver salts and DBU, Synthesis (2010) 1433–1440. [31] Q.W. Song, W.Q. Chen, R. Ma, A. Yu, Q.Y. Li, Y. Chang, L.N. He, Bifunctional silver (I) complex-catalyzed CO2 conversion at ambient conditions: synthesis of α-methylene cyclic carbonates and derivatives, ChemSusChem 8 (2015) 821–827. [32] Q.-W. Song, B. Yu, X.-D. Li, R. Ma, Z.-F. Diao, R.-G. Li, W. Li, L.-N. He, Efficient chemical fixation of CO2 promoted by a bifunctional Ag2WO4/Ph3P system, Green Chem. 16 (2014) 1633–1638. [33] Q.W. Song, Z.H. Zhou, H. Yin, L.N. He, Silver (I)-Catalyzed Synthesis of β-oxopropylcarbamates from propargylic alcohols and CO2 surrogate: a gas-free process, ChemSusChem 8 (2015) 3967–3972. [34] C.-R. Qi, H.-F. Jiang, Efficient synthesis of β-oxopropylcarbamates in compressed CO2 without any additional catalyst and solvent, Green Chem. 9 (2007) 1284–1286.
cores, Beilstein J. Org. Chem. 13 (2017) 625–638; (i) E. Vessally, R. Hosseinzadeh-Khanmiri, E. Ghorbani-Kalhor, M. Es’haghi, A. Bekhradnia, Domino carbometalation/coupling reactions of Narylpropiolamides: a novel and promising synthetic strategy toward stereocontrolled preparation of highly substituted 3-methyleneindolinones, RSC Adv. 7 (2017) 19061–19072; (j) S. Soleimani-Amiri, E. Vessally, M. Babazadeh, A. Hosseinian, L. Edjlali, Intramolecular cyclization of N-allyl propiolamides: a facile synthetic route to highly substituted glactams (a review), RSC Adv. 7 (2017) 19061–19072. A.K. Ghosh, M. Brindisi, Organic carbamates in drug design and medicinal chemistry, J. Med. Chem. 58 (2015) 2895–2940. R.C. Gupta, Toxicology of Organophosphate and Carbamate Compounds, Elsevier, Amsterdam, 2006. (a) J.S. Nowick, N.A. Powell, T.M. Nguyen, G. Noronha, An improved method for the synthesis of enantiomerically pure amino acid ester isocyanates, J. Org. Chem. 57 (1992) 7364–7366. Q.-W. Song, Z.-H. Zhou, L.-N. He, Efficient, selective and sustainable catalysis of carbon dioxide, Green. Chem. (2017), http://dx.doi.org/10.1039/C7GC00199A. Y. Sasaki, P.H. Dixneuf, Ruthenium-catalyzed reaction of carbon dioxide amine, and acetylenic alcohol, J. Org. Chem. 52 (1987) 4389–4391. Y. Gu, Q. Zhang, Z. Duan, J. Zhang, S. Zhang, Y. Deng, Ionic liquid as an efficient promoting medium for fixation of carbon dioxide: a clean method for the synthesis of 5-methylene-1 3-oxazolidin-2-ones from propargylic alcohols, amines, and carbon dioxide catalyzed by Cu (I) under mild conditions, J. Org. Chem. 70 (2005) 7376–7380. H. Jiang, J. Zhao, A. Wang, An efficient and eco-friendly process for the conversion of carbon dioxide into oxazolones and oxazolidinones under supercritical conditions, Synthesis (2008) 763–769. J. Xu, J. Zhao, Z. Jia, J. Zhang, Facile and mild process for chemical fixation of CO2 to 4-methylene-1, 3-oxazolidin-2-ones under solvent-free conditions, Synth. Commun. 41 (2011) 858–863. H.-F. Jiang, J.-W. Zhao, Silver-catalyzed activation of internal propargylic alcohols in supercritical carbon dioxide: efficient and eco-friendly synthesis of 4-alkylidene1 3-oxazolidin-2-ones, Tetrahedron Lett. 50 (2009) 60–62. Q.-W. Song, B. Yu, X.-D. Li, R. Ma, Z.-F. Diao, R.-G. Li, W. Li, L.-N. He, Efficient chemical fixation of CO 2 promoted by a bifunctional Ag 2 WO 4/Ph 3P system, Green Chem. 16 (2014) 1633–1638. Q.W. Song, Z.H. Zhou, M.Y. Wang, K. Zhang, P. Liu, J.Y. Xun, L.N. He, Thermodynamically favorable synthesis of 2-oxazolidinones through silver-catalyzed reaction of propargylic alcohols, CO2, and 2-aminoethanols, ChemSusChem 9
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Journal of CO2 Utilization journal homepage: www.elsevier.com/locate/jcou
Review Article
Three-component coupling of CO2, propargyl alcohols, and amines: An environmentally benign access to cyclic and acyclic carbamates (A Review)
MARK
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Sattar Arshadia, , Esmail Vessallya, Akram Hosseinianb, Somayeh Soleimani-amiric, Ladan Edjlalid a
Departmentof Chemistry, Payame Noor University, Tehran, Iran Department of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran c Department of Chemistry, Karaj Branch, Islamic Azad University, Karaj, Iran d Department of Chemistry, Tabriz Branch, Islamic Azad University, Tabriz, Iran b
A R T I C L E I N F O
A B S T R A C T
Keywords: CO2 Carbamates 2-Oxazolidinones β-Oxoalkyl carbamates Three-component reactions Carbonates Catalyst
Carbamates are key intermediates in the synthesis of a variety of pharmaceutically important compounds and fine chemicals. Moreover, they have been widely applied as chiral auxiliaries in asymmetric transformations. Consequently, much efforts have been devoted to the design and synthesis of these compounds. Synthesis of titled compounds utilizing carbon dioxide as a feedstock is more attractive in comparison to other processes, because CO2 is an abundant, cheap, green, nontoxic, non-flammable, and renewable C1 resource. In this mini review, we highlight the advances in synthesis of cyclic and acyclic carbamates through three-component coupling of CO2, amines and propargyl alcohols from 1987 to 2017.
1. Introduction Global warming is caused by the extensive emission of carbon dioxide (approximately 38000 million tons per year), and therefore, many efforts have been devoted to developing versatile processes to its capture and utilization [1]. Conversely, CO2 can be used as a safe, nontoxic, and inexpensive building block to produce various valuable organic compounds, such as carboxylic acids, esters, alcohols, amides, aldehydes, carbonates, and carbamates [2]. Needless to say, access to organic compounds by multicomponent routes is particularly attractive in terms of synthetic efficiency, and also from the environmental point of view [3]. 2-oxazolidinones (five-membered cyclic carbamates) are one of the most important skeletons which not only show interesting biological and therapeutic activities (Scheme 1) [4], but also used as a building block in organic synthesis [5]. In particular, they have been widely applied as chiral auxiliaries in asymmetric syntheses [6]. Some of the most important methodologies for the preparation of 2-oxazolidione derivatives from CO2 are summarized as follows: (1) chemical fixation of CO2 to substituted aziridines [7]; (2) chemical fixation of CO2 to 2amino alcohols [7]; (3) chemical fixation of CO2 to N-propargylamines [8]; and (4) cycloadditon reaction of propargylic alcohols with primary amines and CO2. Compared to the other methods, cycloaddition reactions of carbon dioxide with propargylic alcohols and amines has remained largely underdeveloped. In continuation of our works on
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synthesis of nitrogen-containing heterocycles from propargylic compounds [9], in the first section of this review, we will highlight the most important developments on synthesis of 2-oxazolidinones through three-component coupling of propargylic alcohols, CO2, and primary amines (Fig. 1, path a), which will be helpful in the development of improved methods for the synthesis of complex and biologically important cyclic carbamates. Acyclic carbamates are widely encountered in the structure of pharmaceuticals [10], and pesticides [11] (Scheme 2). The classical method for the synthesis of carbamates generally involves the use of highly toxic phosgene or isocyanate derivatives as starting material which may cause serious environmental pollution and safety problems [12]. Over the past three decades, CO2 has emerged as an alternative to phosgene and isocyanates in carbamate synthesis. Synthesis of β-oxoalkyl carbamates via three-component coupling of CO2, secondary amines and propargyl alcohols have undergone an explosive growth in recent years (Fig. 1, path b). This new page of carbamate synthesis offers several advantages, such as: (1) nontoxic by-products; (2) high atom economy; (3) ease of handling; (4) cheap and simple starting materials and many more. To the best of our knowledge, a comprehensive review has not appeared on the synthesis of β-oxoalkyl carbamates through three-component reaction of propargylic alcohols, amines, and CO2 in literature so far. The second section of this review will discuss on the synthesis of β-oxoalkyl carbamate derivatives via three-component reaction of propargylic alcohols, secondary amines,
Corresponding author. E-mail addresses: [email protected], [email protected] (S. Arshadi).
http://dx.doi.org/10.1016/j.jcou.2017.07.008 Received 11 May 2017; Received in revised form 13 June 2017; Accepted 5 July 2017 Available online 11 July 2017 2212-9820/ © 2017 Elsevier Ltd. All rights reserved.
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Scheme 1. Selected examples of drugs containing 2-oxazolidione core.
oxazolidinones 10 (Scheme 4). According to the author proposed mechanism this reaction proceeds via the initial formation of an α-alkylene cyclic carbonate B from the starting propargylic alcohol 7 and CO2 through intermediate A. Next, a nucleophilic addition of primary amine 8 to intermediate B occurs to produce 2-oxoalkylcarbamate C, which then undergoes an intramolecular cyclization to produce 4-hydroxy cyclic carbamate D. Finally, a regioselective dehydration takes place to give the expected products 9 and 10 (Scheme 5) [16]. Inspired by these works, the group of J. Zhao developed an analogous one-pot access to 5methylene-2-oxazolidinones 13 by the three-component reaction of tertiary propargylic alcohols 11, primary amines 12, and CO2 at atmospheric pressure under solvent free-conditions using CuCl as catalyst (Scheme 6) [17]. The yields are somewhat lower than those reported by Jiang, but the products could be smoothly achieved under mild conditions. In 2009, Jiang and Zhao reported that the commercially available AgOAc was highly effective catalyst for the cycloaddition reactions of carbon dioxide with internal propargylic alcohols 14 and primary amines 15. Other silver catalysts, such as AgBF4 and Ag2CO3 were also found to promote this three-component reaction; however, in lower yields. The reaction was carried out under supercritical conditions at 120 °C and provided corresponding 2-oxazolidinones 16 in good to excellent yields (Scheme 7). The reaction is noteworthy in that both alkyl and aryl substituted internal propargylic alcohols is tolerated. It should be mentioned that the substitution pattern of starting alcohols had no effect on the regioselectivity of reaction. Thus, it is found that the primary, secondary and tertiary alcohols 14 underwent the reaction smoothly, furnishing the corresponding 2-oxazolidinones 16, without any of oxazolones [18]. Recently W. Li and L. He along with their co-workers were able to demonstrate that a range of 5-methylene-2-oxazolidinones 19 could be obtained from the three-component reaction of tertiary propargylic alcohols 17, primary amines 18 and CO2 at 0.5 MPa pressure under solvent-free conditions employing Ag2WO4 as catalyst and Ph3P as additive. The corresponding 2-oxazolidinones 19 were obtained in 83–95% yields (Scheme 8a). The authors found that this bifunctional
and CO2. Mechanistic aspects of the reactions are considered and discussed in detail. 2. Cyclic carbamates 2.1. Metal catalyzed reactions Chemical fixation of carbon dioxide by metal-catalysts has attracted a lot of attention because of these catalysts allow for rapid transformations under mild conditions with low loading. These flexible catalysts can also be easily separated and reused several times without obvious loss in the catalytic activity and selectivity [13]. In 1987, Sasaki et al. published the first example on the synthesis of cyclic carbamates through metal catalyzed cycloadditon reaction of propargylic alcohols with primary amines and CO2. They showed that the reaction of propargylic alcohols 1 with n-propylamine 2 in the presence of Ru3(CO)12 as catalyst under carbon dioxide atmosphere can produce the corresponding oxazolones 3 in low to moderate yields (Scheme 3a). The results demonstrated that secondary propargylic alcohol 1b was more reactive than primary propargylic alcohol 1a [14]. Eighteen years later, Deng and co-workers were able to extended this chemistry to the synthesis of functionalized 2-oxazolidinones. They found that treatment of tertiary propargylic alcohols 4 with primary amines 5 and CO2 in the presence of cheap and easily accessible CuI as catalyst in [BMIm]BF4 medium produced the corresponding 4-methylene-2-oxazolidinones 6 in high to excellent yields (Scheme 3b). In this study, the authors found some limitations in their methodology when they attempted to react primary and secondary propargylic alcohols. In these cases, they observed no formation of 2-oxazolidinone product. In addition, aniline also failed to form the desired product [15]. Shortly afterwards, Jing, Zhao, and Wang reinvestigated this reaction using CuI as catalyst under supercritical conditions. The author found that the substitution pattern on propargylic alcohols 7 had a fundamental influence on the regioselectivity of reaction. Thus, reaction of primary and secondary propargylic alcohols gave oxazolones 9, whereas reaction of tertiary propargylic alcohols lead to 5-methylene-2-
Fig. 1. Schematic representation of the three-component coupling of CO2, propargyl alcohols, and amines.
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Scheme 2. Chemical structure of some of the marketed drugs and pesticides containing carbamate moiety.
alkylidene cyclic carbonate, azolidinones (Scheme 10) [20].
silver tungstate catalyst simultaneously activate both the propargylic substrate and CO2 which cooperative catalytic mechanism by the silver cation and the tungstate anion (Scheme 8b). It is noted that under this reaction conditions, internal propargylic alcohols failed to form the desired product and secondary alcohols gave the oxazolone derivatives [19]. Very recently, the same research team presented one of the most striking examples of the synthesis of 2-oxazolidinone derivatives 22 via silver-catalyzed three-component cascade reaction of terminal propargylic alcohols 20, 2-aminoethanols 21, and CO2 (Scheme 9). In their optimization study, the authors found that the use of 5 mol% of Ag2CO3 and 10 mol% of Xantphos in chloroform gave the best results. The presence of additive was critical for the success of this reaction, no reaction occurred in the absence of the additive. Under optimized conditions the reaction tolerated a variety of functional groups, such as chloro, methoxy, nitro, and hydroxy functionalities and gave final products in moderate to excellent yields. According to the author proposed mechanism, the reaction proceeds through formation of α-
β-oxopropylcarbamate,
and
2-ox-
2.2. Organocatalyzed reactions Over the last few decades, organocatalysts (organic catalysts) has attracted much attention from both academia and industry, and emerged as one of the hot topics in advanced organic chemistry. These catalysts are often robust, affordable, non-toxic, and insensitive to the air and moisture, and thus are easy to handle. A remarkable number of organocatalysts and processes, such as one-pot, tandem, cascade or multicomponent reactions, have been reported to date [21]. In 1990, the group of Fournier demonstrated for the first time the usefulness of organocatalysts for the cycloadditon reaction of propargylic alcohols with primary amines and CO2. Thus, in the presence of tributylphosphine (Bu3P) as catalyst at 110–140 °C, three component coupling reaction of CO2, 2-methylbut-3-yn-2-ol 24 and primary amines 25 furnished corresponding 5,5-dimethyl-4-methylene-2-oxazolidinones Scheme 3. (a) Ru-catalyzed three-component reaction of propargylic alcohols 1, primary amines 2, and CO2 developed by Sasaki; (b) Synthesis of 4-methylene-2-oxazolidinones 6 through Cu(I)-catalyzed reaction of propargylic alcohols 4, primary amines 5 and CO2.
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Scheme 4. Cu(I)-catalyzed cycloaddition reaction of carbon dioxide with propargylic alcohols 7 and amines 8 to produce oxazolones 9 and 2-oxazolidinones 10.
Scheme 5. Mechanistic proposal for the reaction in Scheme 4.
Scheme 6. Cu(I)-catalyzed three-component reaction of tertiary propargylic alcohols 11, primary amines 12, and CO2.
Scheme 7. Silver-catalyzed cycloaddition reactions of carbon dioxide with internal propargylic alcohols 14 and primary amines 15.
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Scheme 8. (a) Ag2WO4-catalyzed three-component reaction of propargylic alcohols 17, primary amines 18 and CO2; (b) Cooperative catalytic mechanism by the silver cation and the tungstate anion.
Scheme 9. Synthesis of 2-oxazolidinones 22 through Ag-catalyzed three-component reaction of propargylic alcohols 20, CO2, and 2-aminoethanols 21.
Scheme 10. Mechanistic proposal for the reaction in Scheme 9.
26 in moderate to good yields (Scheme 11) [22]. The main advantage of this protocol compared to the metal catalyzed processes is that aromatic amines can be subjected to couplings to give N-aryl 2-oxazolidinone derivatives. Along this line, Costa and co-workers reported the cycloaddition reactions of supercritical carbon dioxide with tertiary propargylic alcohols 27 and primary amines 28 by using bicyclic guanidine catalysts. The reaction tolerates both alkyl and arylamines and gave final product 29 in moderate to good yields (Table 1). The results revealed that the alkylamines are extremely reactive than arylamines. According to
mechanistic studies, it proceeds through the formation of a cyclic carbonate C from the starting tertiary propargylic alcohol 27 and CO2 through intermediates A and B, following the nucleophilic attack of primary amine 28 to the carbonyl group of the intermediate C to give the acyclic carbamate D, which then undergoes a cyclization by intramolecular attack of the amino group to the ketonic carbonyl to produce intermediate E. The last step of the transformation involves the dehydration of E to the final 2-oxazolidinone 29 (Scheme 12) [23]. In a closely related investigation, Liu and Hua disclosed that 2,2′,2”-terpyridine could efficiently catalyze cycloaddition reaction of CO2 with 112
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Scheme 11. Bu3P-catalyzed coupling of 2-methylbut-3-yn-2-ol 24, primary amines 25, and CO2 reported by Fournier.
Table 1 Guanidine-catalyzed synthesis of 2-oxazolidinones 29 from terminal propargylic alcohols 27, primary amines 28, and CO2.
Entry 1 2 3 4 5 6 7 8 9 10 11 12 13
R1 Me Me Me Me Me Me Me Me Me Me -(CH2)5-(CH2)5-(CH2)5-
R2 Me Me Me Me Me Me Me Ph Ph Ph
R3NH2 n-BuNH2 n-BuNH2 butan-2-amine t-BuNH2 allylNH2 BzNH2 PhNH2 n-BuNH2 n-BuNH2 PhNH2 n-BuNH2 n-BuNH2 PhNH2
Catalyst MTBD TBD MTBD MTBD MTBD MTBD MTBD MTBD TBD MTBD MTBD TBD MTBD
Yield (%) 78 78 72 – 72 67 38 72 21 15 69 65 33
Scheme 12. Mechanism proposed to explain the synthesis of substituted 2-oxazolidinones 29 developed by Costa.
Scheme 13. 2,2',2”-terpyridine catalyzed reaction of carbon dioxide with propargylic alcohols 30 and primary amines 31.
2.3. Ionic liquid catalyzed reactions
terminal propargylic alcohols and amines. Under optimized conditions (2,2′,2”-terpyridine, 5 mol%, solvent-free, 140 °C) various propargylic alcohols, including secondary and tertiary alcohols, react to give good yields of the corresponding products (Scheme 13). However, internal propargylic alcohols failed to participate in this reaction [24].
Ionic liquids are salt-like materials that are liquid at unusually low temperatures. They are nonflammable, non-volatile and recyclable and therefore have been widely applied in multitude of areas such as 113
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Scheme 14. Synthesis of 4-methylene-2-oxazolidinones 35 via treatment of tertiary propargylic amines 33 with cyclohexanamine 34 under CO2 atmosphere in ionic liquid.
Scheme 15. (a) Ru-catalyzed synthesis of carbamates 38 developed by Bruncau; (b) Ru3(CO)12mediated synthesis of carbamates 41 reported by Sasaki.
3. Acyclic carbamates 3.1. Metal catalyzed reactions Metal-catalyzed three-component reaction of propargylic alcohols, carbon dioxide, and secondary amines provide powerful and flexible protocols for preparation of acyclic carbamates. These reactions have been abundantly used for synthesis of special β-oxoalkyl carbamate derivatives. One of the earliest reports of the applicability of these reactions, has been reported by Bruncau and Dixncuf in 1987, when terminal propargyl alcohols 36, secondary amines 37, and CO2 underwent a three-component coupling reaction in the presence of [RuCl2(norbornadiene)]n as catalyst in acetonitrile to form carbamate 38 (Scheme 15a) [27]. The desired products were isolated in low to moderate yields. At the same time, Sasaki reported independently a similar strategy for the preparation of β-oxoalkyl carbamates 41 from corresponding propargylic alcohols 39 and amines 40 by using only 1 mol% of Ru3(CO)12 as catalyst in MeCN (Scheme 15b). However, this reaction system also gave low to moderate yields of the desired products [14]. Inspired by these works, the group of Shi described that lanthanide chlorides (Scheme 16a) [28] and iron complexes (Scheme 16b) [29] were good catalysts for this reaction. Just like previous works, the desired products were isolated in low to moderate yields.
Scheme 16. Lanthanide and iron complexes as catalysts for the synthesis of acyclic carbamates from corresponding propargylic alcohols, amines, and CO2.
organic synthesis, catalysis, solar cell, fuel cells, and many more. However, they suffer from some serious drawbacks such as high cost of preparation, and tedious separation and recovery from reaction medium [25]. The reported examples for synthesis of 2-oxazolidinones through ionic liquid catalyzed cycloaddition reactions of carbon dioxide with propargylic alcohols and amines are scarce and to the best of our awareness there is only one example on this chemistry. In 2005, Deng and co-workers showed that the treatment of α,α-disubstituted propargyl alcohols 33 with cyclohexanamine 34 in ionic liquid [DMIm] [BF4] under carbon dioxide atmosphere for 10 h afforded corresponding 4-methylene-2-oxazolidinone derivatives 35 in moderate to high yields (Scheme 14). It should be mentioned that the ionic liquid playing a dual role in this reaction; the solvent and the catalyst [26].
Scheme 17. Ag/DBU-catalyzed synthesis of carbamates 41 reported by Jiang.
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Scheme 18. Mechanistic proposal for the reaction in Scheme 17. Scheme 19. Bifunctional silver(I) complexcatalyzed reaction of terminal propargylic alcohols 45, secondary amines 46, and CO2.
Scheme 20. 1H NMR (a, b) and 13C NMR (c–f) investigation. (a, b) 2-methyl-4-phenylbut-3-yn-2-ol (8.0 mg), Ag2CO3 (2.8 mg) and Ph3P (10.5 mg) ([D6]DMSO 0.6 mL). (c,d) 2methylbut-3-yn-2-ol (20.2 mg), AgNO3 (40.8 mg) (CDCl3 0.6 mL). (e) [(Ph3P)2Ag]2CO3 (158.6 mg) in 0.6 mL of CDCl3. (f) [(Ph3P)2Ag]2CO3 (158.6 mg) in 0.6 mL of CDCl3 in the presence of 13CO2 (1 bar).
reaction is equally efficient for both the aryl and alkyl substituted propargylic alcohols. Other silver catalysts such as AgNO3, AgBF4, and AgCO3 were also found to promote the reaction; however, in lower yields. It is noted that the sterically hindered diisopropylamine failed to afford the product under this reaction conditions. The mechanism proposed by the authors to explain this reaction involves: (1) the Ag(I)/
Nearly two decades after these works, Qi, Huang, and Jiang applied the AgOAc/DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) system to the cycloadditon reaction of internal propargylic alcohols 42 with secondary amines 43 and CO2. The reaction was run in 1,4-dioxane at 90 °C and in most cases, provided carbamates 44 in good to excellent yields (Scheme 17). The results proved that this Ag(I)-catalyzed 115
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Scheme 21. Ag-catalyzed synthesis of βoxoalkyl carbamates 50 from the reaction between a propargylic alcohols 48 and ammonium carbamate 49.
Scheme 22. Proposed mechanism for formation of 47. Table 2 Guanidine-catalyzed synthesis of carbamates 53 under supercritical conditions.
Entry 1 2 3 4 5 6 7 8 9
R1 Me Me Me Me Me H -(CH2)5-(CH2)5-(CH2)5-
R2 Me Me Me Ph Ph H
R32NH pyrrolidine n-Bu2NH n-Bu2NH pyrrolidine n-Bu2NH pyrrolidine pyrrolidine n-Bu2NH n-Bu2NH
Catalyst MTBD MTBD TBD MTBD MTBD MTBD MTBD MTBD TBD
Yield (%) 79 79 58 78 77 33 81 82 48
gram-scale with little effect on the yield. To elucidate the mechanism of this silver (I) complex-catalyzed CO2 conversion, the authors conducted nuclear magnetic resonance (NMR) spectroscopy investigations (Scheme 20). According to data obtained by 1H and 13C NMR techniques, the authors found that this catalyst simultaneously activate propargylic alcohol and CO2 [31]. Ag2WO4 is another successful Ag(I)based bifunctional catalyst that developed by the same authors for this chemistry [32]. Recently, the same research team reported an alternative strategy for the preparation of β-oxoalkyl carbamates 50 from the reaction between an ammonium carbamate 48 (made using CO2 and secondary
DBU catalyzed incorporation of carbon dioxide into the propargylic alcohol 42 which resulted in Z-alkylidene cyclic carbonate C; (2) nucleophilic addition of amine 43 to intermediate C to give allylcarbamate D; and (3) the tautomerization of D to provide β-oxoalkyl-N,Ndialkyl carbamate 44 (Scheme 18) [30]. In 2014, L. He and co-workers developed a PPh3-promoted, Ag2CO3catalyzed three-component reaction of terminal propargylic alcohols 45, secondary amines 46, and CO2, which allowed for the synthesis of acyclic carbamates 47 in good to excellent yields under very mild conditions (atmospheric pressure of CO2 and 30 °C temperature) (Scheme 19). It is noteworthy that this procedure was applied on the 116
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Scheme 23. Catalyst and solvent-free reaction of propargylic alcohols 54, secondary amines 55, and CO2 to β-oxoalkyl carbamate derivatives 56.
amine) and propargylic alcohols 49 using Ag2O/PPh3 combination as catalytic system in acetonitrile at 60 °C (Scheme 21). Beside good yields, simplicity, and relatively mild reaction conditions were other advantages of this gas-free process. The proposed mechanism for this silver-catalyzed two-component reaction is shown in Scheme 22. It consists of the following key steps: (1) initial formation of propargylic carbonate intermediate A via the reaction of propargylic alcohol 48 with ammonium carbamate 49; (2) interchanging of A with silver(I) catalyst to afford the silver propargylic carbonates B; (3) intramolecular 5-exo-cyclization of intermediate B to give intermediate C via an antiaddition mode; (4) proto-demetallation of intermediate C to give the αalkylidene cyclic carbonate D; and (5) nucleophilic attack of secondary amine to the carbonyl group of the intermediate D followed by tautomerization to produce expected products 50 [33].
derivatives. Notably, the formation of cyclic and acyclic carbamate scaffolds depends on the structure of the amine (primary and secondary) employed. Thus, the coupling reaction of CO2, propargyl alcohols and primiary amines gives corresponding cyclic carbamates while the use of secondary amine led to acyclic carbamate derivatives. These reactions have shown both the environmental and economic advantages. It is noteworthy that most of the conversion of CO2 covered in this review could be promoted by earth abundant metal catalysis such as copper and silver as well as organocatalysts demonstrating the greener feature of the present protocol. We hope that this mini review will encourage synthetic organic chemists to employ this valuable and interesting methodology in synthesis of important carbamate derivatives. References
3.2. Organocatalyzed reactions [1] A. Samanta, A. Zhao, G.K. Shimizu, P. Sarkar, R. Gupta, Post-combustion CO2 capture using solid sorbents: a review, Ind. Eng. Chem. Res. 51 (2012) 1438–1463. [2] (a) D. Yu, S.P. Teong, Y. Zhang, Transition metal complex catalyzed carboxylation reactions with CO2, Coord. Chem. Rev. 293 (2015) 279–291. [3] (a) B.B. Toure, D.G. Hall, Natural product synthesis using multicomponent reaction strategies, Chem. Rev. 109 (2009) 4439–4486. [4] (a) I. Berlin, R. Zimmer, H. Thiede, C. Payan, T. Hergueta, L. Robin, A. Puech, Comparison of the monoamine oxidase inhibiting properties of two reversible and selective monoamine oxidase-A inhibitors moclobemide and toloxatone, and assessment of their effect on psychometric performance in healthy subjects, Br. J. Clin. Pharmacol. 30 (1990) 805–816. [5] (a) S.P. Fearnley, 2-(3H)-Oxazolone-A simple heterocycle with manifold potential, Curr. Org. Chem. 8 (2004) 1289–1337. [6] M.M. Heravi, V. Zadsirjan, Oxazolidinones as chiral auxiliaries in asymmetric aldol reactions applied to total synthesis, Tetrahedron: Asymmetry 24 (2013) 1149–1188. [7] S. Pulla, C.M. Felton, P. Ramidi, Y. Gartia, N. Ali, U.B. Nasini, A. Ghosh, Advancements in oxazolidinone synthesis utilizing carbon dioxide as a C1 source, J. CO2 Util. 2 (2013) 49–57. [8] S. Arshadi, E. Vessally, M. Sobati, A. Hosseinian, A. Bekhradnia, Chemical fixation of CO2 to N-propargylamines: a straightforward route to 2-oxazolidinones, J. CO2 Util. 19 (2017) 120–129. [9] (a) E. Vessally, A new avenue to the synthesis of highly substituted pyrroles: synthesis from N-propargylamines, RSC Adv. 6 (2016) 18619–18631; (b) E. Vessally, A. Hosseinian, L. Edjlali, A. Bekhradnia, M.D. Esrafili, New page to access pyridine derivatives: synthesis from N-propargylamines, RSC Adv. 6 (2016) 71662–71675; (c) E. Vessally, A. Hosseinian, A. Bekhradnia, M.D. Esrafili, New page to access pyrazines and their ring fused analogues: synthesis from N-propargylamines, Curr. Org. Synth. 14 (2017) 557–567; (d) E. Vessally, A. Hosseinian, L. Edjlali, A. Bekhradnia, M.D. Esrafili, New route to 1, 4-oxazepane and 1, 4-diazepane derivatives: synthesis from N-propargylamines, RSC Adv. 6 (2016) 99781–99793; (e) E. Vessally, L. Edjlali, A. Hosseinian, A. Bekhradnia, M.D. Esrafili, Novel routes to quinoline derivatives from N-propargylamines, RSC Adv. 6 (2016) 49730–49746; (f) S. Arshadi, E. Vessally, L. Edjlali, E. Ghorbani-Kalhor, R. HosseinzadehKhanmiri, N-Propargylic β-enaminocarbonyls: powerful and versatile building blocks in organic synthesis, RSC Adv. 7 (2017) 13198–13211; (g) E. Vessally, S. Soleimani-Amiri, A. Hosseinian, L. Edjlali, A. Bekhradnia, New protocols to access imidazoles and their ring fused analogues: synthesis from Npropargylamines, RSC Adv. 7 (2017) 7079–7091; (h) S. Arshadi, E. Vessally, L. Edjlali, R. Hosseinzadeh-Khanmiri, E. GhorbaniKalhor, N-Propargylamines: versatile building blocks in the construction of thiazole
With the objective of designing a greener and eco-friendly procedure to β-oxoalkyl carbamates through reaction of propargylic alcohols with secondary amines and CO2, the group of Costa were able to demonstrate that a range of carbamates 53 could be obtained from the reaction of corresponding terminal propargylic alcohols 51 with aliphatic amines 52 in supercritical carbon dioxide employing bicyclic guanidines such as triazabicyclodecene (TBD) and 7-methyl-triazabicyclodecene (MTBD) as cost-effective and non-toxic catalysts (Table 2). The reaction tolerates both primary and tertiary propargylic alcohols and gave final product in moderate to good yields [23]. 3.3. Catalyst-free reactions In 2007, Qi and Jiang discovered that synthesis of β-oxoalkyl carbamate derivatives through three-component reaction of propargylic alcohols, secondary amines, and CO2, are possible even in the absence of any additional catalyst and organic solvent. Thus, treatment of tertiary terminal propargylic alcohols 54 with secondary amines 55 in the presence of compressed CO2 (14 MPa) at 130 °C furnished corresponding acyclic carbamates 56 in moderate to high yields (Scheme 23). The authors proposed that secondary amines playing a dual role in this reaction; the substrate and the catalyst [34]. 4. Conclusion Development of green processes based on chemical fixation of CO2 has received much attention in synthetic organic chemistry in recent years because CO2 is a safe, cheap, abundant, and renewable C1 resource. As shown in this review, one of the useful transformations in which CO2 has been utilized as a substrate is through the three-component coupling of CO2, amines and propargyl alcohols to provide synthetically and biologically important cyclic and acyclic carbamate 117
Journal of CO₂ Utilization 21 (2017) 108–118
S. Arshadi et al.
[10] [11] [12]
[13] [14] [15]
[16]
[17]
[18]
[19]
[20]
(2016) 2054–2058. [21] (a) D.W. MacMillan, The advent and development of organocatalysis, Nature 455 (2008) 304–308. [22] J. Fournier, C. Bruneau, P.H. Dixneuf, A simple synthesis of oxazolidinones in one step from carbon dioxide, Tetrahedron Lett. 31 (1990) 1721–1722. [23] N.D. Ca, B. Gabriele, G. Ruffolo, L. Veltri, T. Zanetta, M. Costa, Effective guanidinecatalyzed synthesis of carbonate and carbamate derivatives from propargyl alcohols in supercritical carbon dioxide, Adv. Synth. Catal. 353 (2011) 133–146. [24] H. Liu, R. Hua, Conversion of carbon dioxide into 2-oxazolidinones and 2 (3H)oxazolones catalyzed by 2 2′, 2″-terpyridine, Tetrahedron 72 (2016) 1200–1204. [25] (a) H. Olivier-Bourbigou, L. Magna, D. Morvan, Ionic liquids and catalysis: recent progress from knowledge to applications, Appl. Catal. A 373 (2010) 1–56. [26] Q. Zhang, F. Shi, Y. Gu, J. Yang, Y. Deng, Efficient and eco-friendly process for the synthesis of N-substituted 4-methylene-2-oxazolidinones in ionic liquids, Tetrahedron Lett. 46 (2005) 5907–5911. [27] C. Bruneau, P.H. Dixncuf, Catalytic synthesis of O-β-oxoalkylcarbamates, Tetrahedron Lett. 28 (1987) 2005–2008. [28] S.-C. Shim, J.-O. Baeg, C.-H. Doh, Y.-Z. Youn, T.-J. Kim, Synthesis of carbamates from amine, acetylenic alcohol, and CO2 using lanthanide as catalyst, Bull. Korean Chem. Soc 11 (1990) 467–468. [29] T.-J. Kim, K.-H. Kwon, S.-C. Kwon, J.-O. Baeg, S.-C. Shim, D.-H. Lee, Iron complexes of 1, 1′-bis (diphenylphosphino) ferrocene (BPPF) as efficient catalysts in the synthesis of carbamates. X-ray crystal structure of (BPPF) Fe (CO)3, J. Organomet. Chem. 389 (1990) 205–217. [30] C. Qi, L. Huang, H. Jiang, Efficient synthesis of β-oxoalkyl carbamates from carbon dioxide, internal propargylic alcohols, and secondary amines catalyzed by silver salts and DBU, Synthesis (2010) 1433–1440. [31] Q.W. Song, W.Q. Chen, R. Ma, A. Yu, Q.Y. Li, Y. Chang, L.N. He, Bifunctional silver (I) complex-catalyzed CO2 conversion at ambient conditions: synthesis of α-methylene cyclic carbonates and derivatives, ChemSusChem 8 (2015) 821–827. [32] Q.-W. Song, B. Yu, X.-D. Li, R. Ma, Z.-F. Diao, R.-G. Li, W. Li, L.-N. He, Efficient chemical fixation of CO2 promoted by a bifunctional Ag2WO4/Ph3P system, Green Chem. 16 (2014) 1633–1638. [33] Q.W. Song, Z.H. Zhou, H. Yin, L.N. He, Silver (I)-Catalyzed Synthesis of β-oxopropylcarbamates from propargylic alcohols and CO2 surrogate: a gas-free process, ChemSusChem 8 (2015) 3967–3972. [34] C.-R. Qi, H.-F. Jiang, Efficient synthesis of β-oxopropylcarbamates in compressed CO2 without any additional catalyst and solvent, Green Chem. 9 (2007) 1284–1286.
cores, Beilstein J. Org. Chem. 13 (2017) 625–638; (i) E. Vessally, R. Hosseinzadeh-Khanmiri, E. Ghorbani-Kalhor, M. Es’haghi, A. Bekhradnia, Domino carbometalation/coupling reactions of Narylpropiolamides: a novel and promising synthetic strategy toward stereocontrolled preparation of highly substituted 3-methyleneindolinones, RSC Adv. 7 (2017) 19061–19072; (j) S. Soleimani-Amiri, E. Vessally, M. Babazadeh, A. Hosseinian, L. Edjlali, Intramolecular cyclization of N-allyl propiolamides: a facile synthetic route to highly substituted glactams (a review), RSC Adv. 7 (2017) 19061–19072. A.K. Ghosh, M. Brindisi, Organic carbamates in drug design and medicinal chemistry, J. Med. Chem. 58 (2015) 2895–2940. R.C. Gupta, Toxicology of Organophosphate and Carbamate Compounds, Elsevier, Amsterdam, 2006. (a) J.S. Nowick, N.A. Powell, T.M. Nguyen, G. Noronha, An improved method for the synthesis of enantiomerically pure amino acid ester isocyanates, J. Org. Chem. 57 (1992) 7364–7366. Q.-W. Song, Z.-H. Zhou, L.-N. He, Efficient, selective and sustainable catalysis of carbon dioxide, Green. Chem. (2017), http://dx.doi.org/10.1039/C7GC00199A. Y. Sasaki, P.H. Dixneuf, Ruthenium-catalyzed reaction of carbon dioxide amine, and acetylenic alcohol, J. Org. Chem. 52 (1987) 4389–4391. Y. Gu, Q. Zhang, Z. Duan, J. Zhang, S. Zhang, Y. Deng, Ionic liquid as an efficient promoting medium for fixation of carbon dioxide: a clean method for the synthesis of 5-methylene-1 3-oxazolidin-2-ones from propargylic alcohols, amines, and carbon dioxide catalyzed by Cu (I) under mild conditions, J. Org. Chem. 70 (2005) 7376–7380. H. Jiang, J. Zhao, A. Wang, An efficient and eco-friendly process for the conversion of carbon dioxide into oxazolones and oxazolidinones under supercritical conditions, Synthesis (2008) 763–769. J. Xu, J. Zhao, Z. Jia, J. Zhang, Facile and mild process for chemical fixation of CO2 to 4-methylene-1, 3-oxazolidin-2-ones under solvent-free conditions, Synth. Commun. 41 (2011) 858–863. H.-F. Jiang, J.-W. Zhao, Silver-catalyzed activation of internal propargylic alcohols in supercritical carbon dioxide: efficient and eco-friendly synthesis of 4-alkylidene1 3-oxazolidin-2-ones, Tetrahedron Lett. 50 (2009) 60–62. Q.-W. Song, B. Yu, X.-D. Li, R. Ma, Z.-F. Diao, R.-G. Li, W. Li, L.-N. He, Efficient chemical fixation of CO 2 promoted by a bifunctional Ag 2 WO 4/Ph 3P system, Green Chem. 16 (2014) 1633–1638. Q.W. Song, Z.H. Zhou, M.Y. Wang, K. Zhang, P. Liu, J.Y. Xun, L.N. He, Thermodynamically favorable synthesis of 2-oxazolidinones through silver-catalyzed reaction of propargylic alcohols, CO2, and 2-aminoethanols, ChemSusChem 9
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