Oxone–acetone mediated Wacker-type oxidation of benzo-fused olefins

Tetrahedron Letters 56 (2015) 3868–3871

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Oxone–acetone mediated Wacker-type oxidation of benzo-fused olefins Ravindra S. Phatake, Chepuri V. Ramana ⇑ Division of Organic Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India

a r t i c l e

i n f o

Article history: Received 2 March 2015 Revised 23 April 2015 Accepted 24 April 2015 Available online 28 April 2015 Keywords: Wacker oxidation Oxone Indene Dihydronaphthalene

a b s t r a c t Herein we disclose a novel application of the oxone–acetone combination for the Wacker-type oxidation of indenes and dihydronaphthalenes leading, respectively, to indan-2-ones and 2-tetralones. The amount of the base employed in the reaction seems to switch the reaction path from dioxygenation to Wackertype oxidation. Control experiments suggest that the reaction is not proceeding via the epoxide route and also that there is no role of trace amounts of metals present in the reagents on the current oxidation. Ó 2015 Elsevier Ltd. All rights reserved.

Epoxidation, dihydroxylation, and oxidation to ketone are some of the important oxidative transformations of olefins that have been well studied since the beginning of organic synthesis.1,2 Among these, the oxidation of olefins directly to carbonyl compounds such as aldehydes and ketones has its own industrial and academic significance.3 The conversion of olefins to carbonyl compounds has been mainly dealt with by employing the complexes of metals such Hg, Pd, Pt, Au, Ru, and Cu.4,5 The Wacker oxidation that uses palladium in combination with copper in the presence of an oxidant is one of the most useful and fundamental reactions in organic synthesis.5 Several modifications have been carried out in recent years that emphasize mainly on the use of green solvents and oxidant free reaction conditions to achieve an effective environment benign method.6 However, methods that employ less hazardous, cost-effective, and metal free oxidation techniques are still warranted.7 Herein, we describe a simple metal-free Wacker-type olefin oxidation employing oxone albeit limited mainly to the benzofused olefins such as indenes and tetralenes. Oxone is a cheap (comparable with hydrogen peroxide and bleach) and easy to handle reagent. Oxone is endorsed with the ability to oxidize a broad spectrum of functional groups.8 Very recently, we have shown that the combination of oxone–acetone, which is well established for the olefin epoxidation reactions, can be used for the cis-dioxygenation of the benzofused olefins leading to a cis-vicinol diol protected as its acetonide.9 We have come across this unusual dioxygenation accidently, while carrying out ⇑ Corresponding author. Tel.: +91 20 2590 2577; fax: +91 20 2590 2629. E-mail address: [email protected] (C.V. Ramana). http://dx.doi.org/10.1016/j.tetlet.2015.04.102 0040-4039/Ó 2015 Elsevier Ltd. All rights reserved.

the preparation of the known indene oxide on multi-gram scales employing the oxone–acetone combination for the epoxidation. A set of two side products (2–3%), namely the indan-2-one 3a and the acetonide 4a along with the required epoxide 2a were obtained under the described conditions (Fig. 1).10 In our previous communication, we have documented a successful realization of the conditions for the direct conversion of indene 1a–4a. With this, we next looked at the possibility of the Wacker-type oxidation of 1a leading directly to 3a. During our previous investigations on the dioxygenation of 1a, it has been found that the indan-2-one was isolated as a single product in 35% yield when the oxidation was performed in 0.5 equiv of oxone in the presence of 3 equiv of NaHCO3 (Table S1 in SI). In order to have a suitable reaction condition for the exclusive formation of 2-indanone, some logical experimentation has been put forward. Optimization experiments have been conducted by varying the proportions of both oxidant and base. The progress and the nature of the intermediates involved in this process have been analyzed with the help of GC–MS. In general, a noticeable change in the consumption of starting material with the product formation was observed with the variation especially in the amounts of base employed (Scheme 1). To this end, the use of 12 equiv of NaHCO3 along with 2 equiv of oxone was found to be the best combination for the complete conversion. Under these optimized conditions, 2-indanone 3a was obtained in 78% yield at room temperature over the period of 15–20 h. However, no further improvement was observed by increasing the quantity of either oxidant and/or base. Also, prolonging the reaction for longer durations had no effect. Control

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R. S. Phatake, C. V. Ramana / Tetrahedron Letters 56 (2015) 3868–3871

Oxone (2 eq.) NaHCO3 (5 eq.) acetone (10 eq.) H 2O:EtOAc (1:1) reported by others

Table 1 Scope of oxone–acetone mediated Wacker-type oxidation of indene derivativesa

O

Entry

2a

previous work

O O

70

1

1b

4-10 h

3b

4a

present work acetone:EtOAC:H 2 O (5:1:1), rt NaHCO3 (12 eq.) reports from our group

Yieldb (%)

Product

O

NaHCO3 (3 eq.)

Oxone (2 eq.)

1a

Substrate

O 74

2

3c

1c

O

15-20 h 3a

Figure 1. Solvent and/or base dependent complementary oxidation of indene with oxone.

O 3

Cl

74

Cl

3d

1d

O 4

N3

O

N3

3e

1e 1a

72

3a

O 5

61

Ph

Ph

1f

3f O 75

6

Ph

Ph

3g

1g

O 78

7

Ph

Ph

3g

1h 8 Scheme 1. Selected conditions explored for the Wacker-type oxidation. Reagents and conditions: All the reactions were carried out at rt with 0.5 mmol of indene in 2.5 ml acetone and 0.5 ml of (1:1 of H2O + EtOAc); (A) oxone (0.5 equiv), NaHCO3 (3 equiv); (B) oxone (1.0 equiv), NaHCO3 (6 equiv); (C) oxone (1.5 equiv), NaHCO3 (9 equiv); (D) oxone (2.0 equiv), NaHCO3 (12 equiv).

3i

O

9

1j experiments revealed that the acetone/H2O/EtOAc (5:1:1) employed for syn-dioxygenation was also found to be the best solvent combination system for the current Wacker-type oxidation. The optimized reaction conditions involve the addition of 2 equiv of powdered oxone to a stirred slurry of 12 equiv of NaHCO3 and 1 equiv indene in a mixture of solvents (5:1:1 acetone/water/ethyl acetate) stirred at room temperature over the prescribed time. The oxidation of simple indene 1a under this condition provided the required 3a in 78% yield as the sole product in 18 h. The scope of this reaction has been generalized by employing various substituted indene derivatives 1b–1h. In general, the reactions proceeded smoothly and provided exclusively corresponding 2-indanones in good yields. As shown in Table 1, the substitution at the C3 (1b–1g) and at C1 position (1h) of indene has little effect on the outcome of the reaction (in terms of yields and the regioselectivity) and proceeded smoothly. This suggested that the reaction is highly regioselective in nature. As expected, the C-1 substituted indene 1h (1-benzyl-1H-indene) and the C-3 substituted 1g (3-benzyl-1H-indene) led to the formation of 1-benzyl-1H-inden-2(3H)-one (3g). Gratifyingly, the reaction conditions

71

O

1i

65

3j

MeO

MeO

10

O

3k

1k

O

11

76

Ph

Ph

3l

1l MeO

MeO

O

12

3m

1m

O p-tolyl

1n

70

Ph

Ph

13

61

p-tolyl

72

3n (continued on next page)

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R. S. Phatake, C. V. Ramana / Tetrahedron Letters 56 (2015) 3868–3871

Oxone (2eq.) NaHCO3 (12eq.)

Table 1 (continued) Entry

Substrate

b

Product

MeO

Yield (%)

MeO 1p

O

14

p-tolyl

1o

p-tolyl

employed was found to be tolerable for a range of functional groups like chloro and azide without affecting the yields of the final products much (Table 1). To explore the scope of this reaction, we next examined the oxidation of 1,2-dihydronaphthalene leading to 2-tetralones. 2Tetralones have been found to have a wide range of applications as valuable intermediates in natural products synthesis and also in the synthesis of pharmaceuticals.11 The 1,2-transposition of the carbonyl group of a-tetralones is one of the generally adopted direct methods for the preparation of b-tetralones.12 Also, the 1,2dihydronaphthalene derivatives have been converted into 2-tetralones by employing a sequence of hydroboration followed by oxidation of the resulting alcohols.13 The 1,2-dihydronaphthalenes 1i–1o have been synthesized following the established procedures and then subjected for the oxone–acetone mediated olefin oxidation under the established conditions. As shown in Table 1 (entries 8–14), in all the cases, the reaction proceeded efficiently and provided the corresponding 2-tetralones with complete regioselectivity. It is worth mentioning here that tetralones 3k and 3n have been prepared earlier in the context of synthesis of an ABCD tetracyclic Bruceantin precursor and a 2 step protocol has been employed.14 In order to have preliminary information on the course of this oxidation reaction, some control experiments have been carried out. At first, both epoxide 2a and acetonide 4a have been exposed to the present conditions for a longer period. It has been found that both 2a and 4a are intact which indicated that either epoxide or the acetonide are not involved as intermediates in the current transformation. Indeed, the GC–MS monitoring of this reaction during the optimization studies has clearly indicated that none of these intermediates are present. Next, the oxidation of 1a has been conducted employing excess QuadraPure™ DMA (a known

O O 4a

No Reaction

acetone:EtOAC:H 2O (5:1:1), rt, 24 h

2a

Oxone (2 eq.) NaHCO3 (12 eq. )

1q

3q (68%) PdCl2 (10 mol %) Cu(OAc) 2 (1.2 eq.)

1q

O2 balloon pressure CH 3CONMe2 :H2 O (4:1) rt, 10 h

O

5 (62%)

Scheme 3. Regioselectivity of Wacker-type oxidation of diene 1p and 1q.

scavenger for metals such as Pd, Cu(I), Cu(II), Ni, Pt, etc.) as an additive in the reaction medium.15 As shown in Scheme 2, there was no interference from this added metal scavenger and there was no change either in the time or the yield of the product. This control experiment has precisely ruled out the possible involvement of traces of metal impurities present in the reagents in the present oxidation. Next, examined was the olefin selectivity of the present process. 3-(but-3-en-1-yl)-1H-indene (1q) and 3-allyl-1H-indene (1p) have been subjected for the present oxidation under established conditions. Interestingly, the oxidation of both dienes 1p and 1q occurred in a way such that the internal olefins only got oxidized resulting in the corresponding indan-2-ones exclusively (Scheme 3). Interestingly, when 1q was exposed to Pd-catalyzed Wacker oxidation, the exclusive oxidation of the external olefin without disturbing the internal olefin has been noticed. This complementary selectivity clearly explains that the oxone–acetone mediated oxidation is very selective for the benzo-fused olefins despite the fact that this olefin is sterically hindered. To conclude, we have documented the direct oxidation of indenes and 1,2-dihydronapthalenes, respectively, to the corresponding 2-indanones and 2-tetralones employing oxone–acetone and sodium bicarbonate under relatively simple conditions. The control experiments primarily reveal that the current reaction is similar to the acetonide formation and did not occur due to the presence of trace-metal impurities, nor is the epoxide an intermediate in the path of the reaction. However, further investigation is underway in our laboratory to rule out the other possibilities. In a nutshell, it must be noted that a subtle variation in the reaction conditions either in terms of the solvents employed and/or the amount of base used seems to causes a complete change in the course of the reaction. The current base-driven switching in reaction path is very unusual and creates substantial opportunities for further exploration. Acknowledgments The authors would like to acknowledge the CSIR (India) for providing the financial support for this project under the NICE (CSC0109). Financial support from CSIR (New Delhi) in the form of a research fellowship to R.S.P. is gratefully acknowledged.

Oxone (2 eq.) NaHCO3 (12 eq. )

1a

O

No Reaction

acetone:EtOAC:H 2 O (5:1:1), rt, 24 h

acetone:EtOAC:H 2 O (5:1:1), rt, 20 h QuadraPure DMA

3p (69%)

''

3o

Oxone (2 eq.) NaHCO3 (12 eq. )

O

69

Reaction conditions. a Substrate 1 (1 equiv), oxone (2 equiv), NaHCO3 (12 equiv), acetone/H2O/EtOAc (5:1:1), rt, 15–20 h. b Isolated yields.

O

acetone:H 2 O:EtOAc (5:1:1) rt, 20h

O

Supplementary data 3a (72%)

Scheme 2. Control experiments conducted to examine the involvement of epoxide and trace metal impurities.

Supplementary data (the NMR spectra of all new compounds) associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.tetlet.2015.04.102.

R. S. Phatake, C. V. Ramana / Tetrahedron Letters 56 (2015) 3868–3871

References and notes 1. (a) Backvall, J.-E. Modern Oxidation Methods; Wiley-VHC: Weinheim, Germany, 2004; (b) March, J. Advanced Organic Chemistry, 4th ed.; Wiley: New York, 1992. pp 734–878; (c) Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry, 3rd ed.; Plenum: New York, 1990. pp 624–642. 2. (a) Matsumoto, M. J. Synth. Org. Chem. JPN 1985, 43, 753–763; (b) PedragosaMoreau, S.; Archelas, A.; Furstoss, R. Tetrahedron 1996, 52, 4593–4606; (c) Bonini, C.; Righi, G. Tetrahedron 2002, 58, 4981–5021; (d) Kowalski, G.; Pielichowski, J. Synlett 2002, 2107–2109; (e) Muzart, J. J. Mol. Catal. A: Chem. 2007, 276, 62–72; (f) Rao, T. S. S.; Awasthi, S. J. Indian Chem. Soc. 2007, 84, 902– 913; (g) Toda, H.; Imae, R.; Itoh, N. Tetrahedron: Asymmetry 2012, 23, 1542– 1549; (h) Wu, W.; Jiang, H. Acc. Chem. Res. 2012, 45, 1736–1748. 3. (a) Smidt, J. Chem. Ind. 1962, 54–61; (b) Sonoda, N. J. Synth. Org. Chem. JPN 1972, 30, 739; (c) Tsuji, J. Synthesis 1984, 369–384; (d) Ranu, B. C.; Chakraborty, R. Synth. Commun. 1990, 20, 1751–1756; (e) Zhang, X. K.; Sullivan, D.; van Hal, J. Arab. J. Sci. Eng. 1999, 24, 101–113; (f) Wang, S. B.; Murata, K.; Hayakawa, T.; Hamakawa, S.; Suzuki, K. J. Chem. Technol. Biotechnol. 2001, 76, 265–272; (g) Muzart, J. Tetrahedron 2007, 63, 7505–7521; (h) Kotali, A.; Lafazanis, I. S.; Harris, P. A. Synthesis 2009, 836–840; (i) Wickens, Z. K.; Morandi, B.; Grubbs, R. H. Angew. Chem., Int. Ed. 2013, 52, 11257–11260. 4. (a) Kano, S.; Yokomatsu, T.; Ono, T.; Hibino, S.; Shibuya, S. J. Chem. Soc., Chem. Commun. 1978, 414–415; (b) Mihara, J.; Hamada, T.; Takeda, T.; Irie, R.; Katsuki, T. Synlett 1999, 1160–1162; (c) Robinson, M. W. C.; Pillinger, K. S.; Mabbett, I.; Timms, D. A.; Graham, A. E. Tetrahedron 2010, 66, 8377–8382; (d) Boisvert, L.; Goldberg, K. I. Acc. Chem. Res. 2012, 45, 899–910; (e) Wang, Z.-M.; Sang, X.-L.; Che, C.-M.; Chen, J. Tetrahedron Lett. 2014, 55, 1736–1739. 5. (a) Miller, D. G.; Wayner, D. D. M. J. Org. Chem. 1990, 55, 2924–2927; (b) Lai, J. Y.; Shi, X. X.; Dai, L. X. J. Org. Chem. 1992, 57, 3485–3487; (c) Higuchi, M.; Yamaguchi, S.; Hirao, T. Synlett 1996, 1213; (d) Li, H. M.; Shu, H. M.; Ye, X. K.; Wu, Y. Progr. Chem. 2001, 13, 461–471; (e) Mitsudome, T.; Umetani, T.; Nosaka, N.; Mori, K.; Mizugaki, T.; Ebitani, K.; Kaneda, K. Angew. Chem., Int. Ed. 2006, 45, 481–485; (f) Cornell, C. N.; Sigman, M. S. Inorg. Chem. 2007, 46, 1903–1909; (g) Keith, J. A.; Henry, P. M. Angew. Chem., Int. Ed. 2009, 48, 9038–9049; (h) Michel, B. W.; Camelio, A. M.; Cornell, C. N.; Sigman, M. S. J. Am. Chem. Soc. 2009, 131, 6076; (i) Winston, M. S.; Oblad, P. F.; Labinger, J. A.; Bercaw, J. E. Angew. Chem., Int. Ed. 2012, 51, 9822–9824; (j) Wang, Y.-F.; Gao, Y.-R.; Mao, S.; Zhang, Y.-L.; Guo, D.-D.; Yan, Z.-L.; Guo, S.-H.; Wang, Y.-Q. Org. Lett. 2014, 16, 1610–1613. 6. (a) Monflier, E.; Tilloy, S.; Blouet, E.; Barbaux, Y.; Mortreux, A. J. Mol. Catal. A: Chem. 1996, 109, 27–35; (b) Ansari, I. A.; Joyasawal, S.; Gupta, M. K.; Yadav, J. S.; Gree, R. Tetrahedron Lett. 2005, 46, 7507–7510; (c) Cornell, C. N.; Sigman, M. S. Org. Lett. 2006, 8, 4117–4120; (d) Yadav, J. S.; Reddy, G. S. K. K.; Sabitha, G.;

7.

8.

9. 10. 11.

12.

13. 14.

15.

3871

Krishna, A. D.; Prasad, A. R.; Hafeez Ur, R.; Rao, K. V.; Rao, A. B. Tetrahedron: Asymmetry 2007, 18, 717–723; (e) Kulkarni, M. G.; Bagale, S. M.; Shinde, M. P.; Gaikwad, D. D.; Borhade, A. S.; Dhondge, A. P.; Chavhan, S. W.; Shaikh, Y. B.; Ningdale, V. B.; Desai, M. P.; Birhade, D. R. Tetrahedron Lett. 2009, 50, 2893– 2894; (f) Escola, J. M.; Botas, J. A.; Vargas, C.; Bravo, M. J. Catal. 2010, 270, 34– 39; (g) Michel, B. W.; Steffens, L. D.; Sigman, M. S. J. Am. Chem. Soc. 2011, 133, 8317–8325; (h) Bigi, M. A.; White, M. C. J. Am. Chem. Soc. 2013, 135, 7831– 7834; (i) DeLuca, R. J.; Edwards, J. L.; Steffens, L. D.; Michel, B. W.; Qiao, X.; Zhu, C.; Cook, S. P.; Sigman, M. S. J. Org. Chem. 2013, 78, 1682–1686; (j) Zhang, G.; Xie, X.; Wang, Y.; Wen, X.; Zhao, Y.; Ding, C. Org. Biomol. Chem. 2013, 11, 2947– 2950; (k) Fernandes, R. A.; Bethi, V. Tetrahedron 2014, 70, 4760–4767; (l) Fernandes, R. A.; Chaudhari, D. A. J. Org. Chem. 2014, 79, 5787–5793. (a) Hermans, I.; Janssen, K.; Moens, B.; Philippaerts, A.; Van Berlo, B.; Peeters, J.; Jacobs, P. A.; Sels, B. F. Adv. Synth. Catal. 2007, 349, 1604–1608; (b) Michel, B. W.; Sigman, M. S. Aldrichim. Acta 2011, 44, 55–62; (c) Nobuta, T.; Hirashima, S.I.; Tada, N.; Miura, T.; Itoh, A. Org. Lett. 2011, 13, 2576–2579; (d) Ahmad, A.; Scarassati, P.; Jalalian, N.; Olofsson, B.; Silva, L. F., Jr. Tetrahedron Lett. 2013, 54, 5818–5820; (e) Harikrishna, K.; Mukkamala, R.; Hinkelmann, B.; Sasse, F.; Aidhen, I. S. Eur. J. Org. Chem. 2014, 2014, 1066–1075; (f) Yang, Q.; Mao, L.-L.; Yang, B.; Yang, S.-D. Org. Lett. 2014, 16, 3460–3463; (g) Rajbongshi, K. K.; Hazarika, D.; Phukan, P. Tetrahedron Lett. 2015, 56, 356–358. (a) Hussain, H.; Green, I. R.; Ahmed, I. Chem. Rev. 2013, 113, 3329–3371; (b) Parent, A. R.; Crabtree, R. H.; Brudvig, G. W. Chem. Soc. Rev. 2013, 42, 2247– 2252; (c) Murray, R. W. Chem. Rev. 1989, 89, 1187–1201; (d) Adam, W.; Curci, R.; Edwards, J. O. Acc. Chem. Res. 1989, 22, 205–211. Phatake, R. S.; Ramana, C. V. Tetrahedron Lett. 2015, 56, 2183–2186. Hashimoto, N.; Kanda, A. Org. Process Res. Dev. 2002, 6, 405–406. (a) Rice, L. M.; Scott, K. R.; Grogan, C. H. J. Med. Chem. 1966, 9, 765; (b) Reddy, J.; Tschaen, D.; Shi, Y. J.; Pecore, V.; Katz, L.; Greasham, R.; Chartrain, M. J. Ferment. Bioeng. 1996, 81, 304–309; (c) Anjanamurthy, C.; Basavaraju, Y. B. Indian J. Chem., Sect B 1999, 38, 137–140; (d) Sadashivamurthy, B.; Basavaraju, Y. B.; Sathisha, A. D.; Hemakumar, K. H. Bulg. Chem. Commun. 2007, 39, 264–268. (a) Fristad, W. E.; Bailey, T. R.; Paquette, L. A. J. Org. Chem. 1978, 43, 1620–1623; (b) Hauser, F. M.; Prasanna, S. Synthesis 1980, 621–623; (c) Braun, M.; Bernard, C. Liebigs Ann. Chem. 1985, 435–437. Kirkiacharian, B. S.; Koutsourakis, P. G. Synth. Commun. 1993, 23, 737–742. (a) Packer, R. A.; Whitehurst, J. S. J. Chem. Soc., Chem. Commun. 1975, 757–758; (b) Suryawanshi, S. N.; Fuchs, P. L. J. Org. Chem. 1986, 51, 902–921; (c) Hedstrand, D. M.; Byrn, S. R.; McKenzie, A. T.; Fuchs, P. L. J. Org. Chem. 1987, 52, 592–598. Hinchcliffe, A.; Hughes, C.; Pears, D. A.; Pitts, M. R. Org. Process Res. Dev. 2007, 11, 477–481.