Rhodium-catalyzed cyclic carbonylation of 2-phenylethynylbenzamide under water–gas shift reaction conditions

www.elsevier.nl/locate/ica Inorganica Chimica Acta 296 (1999) 195 – 203

Rhodium-catalyzed cyclic carbonylation of 2-phenylethynylbenzamide under water–gas shift reaction conditions Shi-Wei Zhang, Takayuki Kaneko, Eiji Yoneda, Takashi Sugioka, Shigetoshi Takahashi * Institute of Scientific and Industrial Research, Osaka Uni6ersity, Ibaraki, Osaka 567 -0047, Japan Received 17 June 1999; accepted 30 August 1999

Abstract Under water–gas shift reaction conditions, Rh6(CO)16-catalyzed carbonylation of 2-phenylethynylbenzamide (1a) gave two kinds of products, novel spiro compound (2a) and 2(5H)-furanone (3a), which were produced by cyclic carbonylation of a carboncarbon triple bond and the former product is formed by participation of the amide group adjacent to the carboncarbon triple bond in the cyclization. The reaction of 2-naphthylethynylbenzamide (1h) afforded the corresponding spiro compound 2h and two furanones 3h and 4h. Furanone 4h is a structural isomer of 3h and was demonstrated to be a precursor of 2h. © 1999 Elsevier Science S.A. All rights reserved. Keywords: Rhodium catalyst; Cyclic carbonylation; Spiro compound; Furanone

1. Introduction Cyclic carbonylation catalyzed by transition metal complexes is one of the most important reactions in carbonylation chemistry, because the reaction in general provides a convenient and effective one-step process for the synthesis of heterocyclic compounds, which are useful intermediates leading to bioactive substances [1]. Such representative examples involve the cyclic carbonylations of unsaturated alcohols and amines [2], and alkynes [3], giving lactones and lactams, respectively. We have also reported the rhodium-catalyzed cyclic carbonylation of alkynes giving furan-2(5H)-ones under water–gas shift reaction (WGSR) conditions (Eq. (1)) [4]. In our reactions, furanones were formed by the incorporation of one molecule of alkyne, two molecules of carbon monoxide, and one molecule of hydrogen originating from water. This carbonylation is characteristic of the WGSR conditions and the similar reaction under syn gas (CO +H2) conditions only yielded hydroxy methylation products from alkynes. * Corresponding author. Fax: +81-6-68798459.

(1) Recently, we have examined the carbonylation of alkynes bearing functional groups such as amino, hydroxyl, formyl and alkoxycarbonyl groups adjacent to the carboncarbon triple bond under WGSR conditions [5]. These reactions provide a diversity of heterocyclic products which arise from the participation of the functional groups in the cyclization. We now report a new cyclic carbonylation of alkynes which bear an amide group adjacent to the carboncarbon triple bond to give novel spiro compounds and 2(5H)-furanones.

2. Experimental Melting points were recorded on a Yamato Model MP-21 melting point apparatus and are uncorrected. IR spectra were obtained with a Perkin–Elmer 2000 infrared spectrophotometer. NMR spectra were

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recorded on a Jeol JNM-LA400 FT NMR system in CDCl3 with tetramethylsilane as an internal standard. Mass spectra were obtained using a Shimadzu GCMSQP2000 spectrometer. Elemental analyses were performed by the Material Analysis Center, ISIR, Osaka University. Analytical HPLC was performed on a Shimadzu GC-12A with a Nakarai 5SL column (4.6× 250 mm).

2.1. Materials Solvents and reagents were purified prior to use according to standard procedures. Rh6(CO)16 was prepared by a method described in the literature [6]. Twosubstituted phenylacetylenes were prepared by a palladium-catalyzed cross-coupling reaction between Two-substituted bromobenzenes and terminal acetylenes by the procedure developed in our laboratory [7]. All other chemicals are commercially available reagents and were used without purification.

2.2. General preparation of ethynyl compounds 1a –g Compounds 1a and 1e were prepared by method A: (1) To a mixture of acetylenic compound (30 mmol) and 2-bromobenzonitrile (20 mmol) in triethylamine (150 ml) were added PdCl2(PPh3)2 (0.3 mmol), PPh3 (1.2 mmol), and CuI (1.7 mmol). The mixture was stirred at 80°C for 12 h under nitrogen and then the solvent was removed under reduced pressure. The resulting residue was passed through a silica gel column with hexane–benzene (7:1) and then AcOEt – hexane (1:1) as an eluent to give the corresponding ethynylbenzonitrile. (2) The mixture of ethynylbenzonitrile (15 mmol) thus obtained, Na2CO3 (3N, 90 ml) and H2O2 (30%, 90 ml) in acetone (90 ml) was stirred at room temperature for 24 h. After removal of the solvent, the residue was diluted by water and extracted with AcOEt. Recrystallization from AcOEt – hexane gave 2phenylethynylbenzamide (1a) and 2-(4-methoxyphenyl)ethynylbenzamide (1e).

2.2.1. 2 -Phenylethynylbenzamide (1a) Colorless crystals (89% yield); m.p. 157°C. IR (KBr): 1651 cm − 1(nCO), 2216 cm − 1 (nCC), 3176 cm − 1 (nNH); 1 H NMR (CDCl3): 7.38 – 7.65 (m, 9H, aromatic ring), 8.11 –8.14 (m, 2H, NH2); 13C NMR (CDCl3): 168.3, 134.6, 133.5, 131.5, 131.0, 130.3, 129.2, 128.8, 128.6, 122.1, 120.2, 95.8, 87.7; MS, m/z 221 (M+). Anal. Calc. for C15H11NO: C, 81.43; H, 5.01; N, 6.33. Found: C, 81.50; H, 4.81; N, 6.23%. 2.2.2. 2 -(4 -Methoxyphenylethynyl)benzamide (1e) Colorless crystals (50% yield); m.p. 151°C. IR (KBr): 1634 cm − 1 (nCO), 2213 cm − 1 (nCC), 3207 cm − 1 (nNH); 1 H NMR (CDCl3): 8.14 (d, 1H, J =9.2 Hz), 7.61 (d,

1H, J= 9.3 Hz), 7.50–7.43 (m, 4H, arom), 6.91 (d, 2H, J= 8.6 Hz), 5.78 (br, 2H, NH2), 3.85 (s, 3H, OCH3); 13 C NMR (CDCl3): 168.3, 160.3, 134.2, 133.3, 133.1, 131.0, 130.3, 128.5, 120.5, 114.2, 114.0, 96.1, 86.5, 55.4; MS m/z 251 (M+). Anal. Calc. for C16H13NO2: C, 76.47; H, 5.21; N, 5.57. Found: C, 76.21; H, 4.99; N, 5.33%. Compounds 1b, 1c and 1d were prepared by method B: (1) Methylamine (30 ml, 40% in water) was added dropwise to a solution of 2-iodobenzoyl chloride (16 mmol) in THF (40 ml). The solution was stirred at room temperature for 30 min. After removal of the solvent, the residue was diluted with H2O and extracted with AcOEt. Recrystallization from AcOEt–hexane gave N-methyl-2-iodobenzamide (95% yield). (2) A mixture of N-methyl-2-iodobenzamide (13 mmol) and phenylacetylene (25 mmol) in the presence of PdCl2(PPh3)2 (0.3 mmol) and CuI (1.7 mmol) in Et2NH (150 ml) was stirred for 12 h at room temperature. After removal of the solvent under reduced pressure, the residue was passed through a silica gel column with benzene and then AcOEt. The solvent was evaporated to give 1b. By Method B, 1c, 1d, 1f, 1g and 1h were also prepared.

2.2.3. N-Methyl-2 -phenylethynylbenzamide (1b) Colorless crystals (3.02 g, 99%); m.p. 104°C. IR (KBr): 3296, 3061, 1645, 1539 cm − 1; 1H NMR (CDCl3): 8.06–8.02 (m, 1H, arom), 7.61–7.58 (m, 1H, arom), 7.54–7.51 (m, 2H, arom), 7.46–7.43 (m, 2H, arom), 7.42–7.39 (m, 3H, arom), 7.39 (br, 1H, NH), 1.56 (d, 3H, J= 26.8 Hz, CH3); 13C NMR (CDCl3): 167.2, 135.9, 133.2, 131.5, 130.4, 129.8, 129.1, 128.8, 128.6, 122.2, 119.5, 95.3, 87.61, 26.8; MS m/z 283 (M+). Anal. Calc. for C16H13NO: C, 81.68; H, 5.57; N, 5.95. Found: C, 81.94; H, 5.28; N, 5.73%. 2.2.4. N-Phenyl-2 -phenylethynylbenzamide (1c) Colorless crystals (97% yield); m.p. 162°C, IR (KBr): 3356, 2346, 1740 cm − 1; 1H NMR (CDCl3): 9.20 (br, 1H, NH), 8.17–8.15 (m, 1H, arom), 7.68–7.66 (m, 3H, arom), 7.52–7.50 (m, 4H, arom), 7.40–7.432 (m, 5H, arom), 7.16–7.13 (m, 1H, arom); 13C NMR (CDCl3): 164.3, 137.9, 135.8, 133.5, 131.7, 130.9, 130.4, 129.3, 129.1, 128.6, 128.3, 124.5, 121.8, 119.9, 119.5, 96.6, 87.2; MS m/z 297 (M+). Anal. Calc. for C21H15NO: C, 84.83; H, 5.08; N, 4.71. Found: C, 85.10; H, 5.02; N, 4.91%. 2.2.5. N,N-Dimethyl-2 -phenylethynylbenzamide (1d) Colorless oil (96% yield). IR (neat): 1646 cm − 1; 1H NMR (CDCl3): 7.55–7.31 (m, 9H, arom), 3.19 (s, 3H, CH3), 2.92 (s, 3H, CH3); 13C NMR (CDCl3): 170.1, 139.6, 131.8, 131.5, 128.7, 128.7, 128.5, 128.4, 126.5, 122.8, 120.1, 92.5, 86.6, 38.4, 34.8; MS m/z 307 (M+). Anal. Calc. for C17H15NO: C, 81.90; H, 6.06; N, 5.61. Found: C, 81.64; H, 6.03; N, 5.50%.

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2.2.6. 2 -(4 -Cyanophenylethynyl)benzamide (1f) Colorless crystals (80% yield). m.p. 167°C. IR (KBr): 3299, 3198, 2230, 1651 cm − 1; 1H NMR (CDCl3): 9.20 (br, 1H, NH), 8.02– 8.01 (m, 1H, arom), 7.69 – 7.57 (m, 5H, arom), 7.52–7.50 (m, 2H, arom), 6.91 (br, 1H, NH), 5.94 (br, 1H, NH); 13C NMR (CDCl3): 168.4, 135.6, 133.6, 132.8, 132.2, 132.1, 131.0, 129.8, 129.6, 129.0, 127.1, 119.3, 118.3, 93.3, 91.5; MS m/z 246 (M+). Anal. Calc. for C16H10N2O: C, 78.04; H, 4.09; N, 11.38. Found: C, 78.30; H, 4.16; N, 11.29%. 2.2.7. 2 -(Mesitylethynyl)benzamide (1g) Colorless crystals (54% yield). IR (KBr): 3368, 3191, 2346, 1654 cm − 1; 1H NMR (CDCl3): 8.31 (d, 1H, J= 7.8 Hz, arom), 7.63 (d, J = 7.3 Hz, arom), 7.54 (m, 2H, arom), 6.92 (m, 2H, arom), 5.72 (br, 2H, NH2), 2.48 (s, 6H, 2CH3), 2.31 (s, 3H, CH3); MS m/z 263 (M+). 2.2.8. 2 -(1 -Naphthylethynyl)benzamide (1h) Colorless crystals (31% yield); m.p. 180°C. IR (KBr): 3368, 3191, 2346, 1654 cm − 1; 1H NMR (CDCl3): 8.41 (d, 1H, J =7.8 Hz), 8.15 (d, 1H, J = 7.3 Hz), 7.92– 7.7.889 (m, 2H), 7.77 (t, 2H, J = 7.3 Hz), 7.65 – 7.47 (m, 5H); 13C NMR (CDCl3): 168.3, 134.7, 133.6, 133.2, 133.2, 131.1, 130.8, 130.3, 129.7, 128.9, 128.5, 127.3, 126.7, 125.8, 125.2, 120.4, 119.7, 94.0, 92.2; MS m/z 271 (M+). Anal. Calc. for C19H13NO: C, 84.11; H, 4.89; N, 5.12. Found: C, 83.90; H, 4.56; N, 5.36%. 2.3. General procedure for carbonylation of ethynyl compounds 1a–h A mixture of ethynyl compound 1 (1 mmol), Rh6(CO)16 (0.0032 mmol), NEt3 (1.4 mmol), and H2O (5.5 mmol) in 1,4-dioxane (15 ml) was placed in a 100 ml stainless-steel autoclave and stirred under 100 atm. of carbon monoxide at 80°C for 3 days. After removal of the solvent from the reaction mixture under reduced pressure, TLC analysis of the residue showed formation of two or three kinds of products, which were separated by column chromatography on silica gel with an eluent of AcOEt–hexane to give products 2, 3 and 4. They were purified by recrystallization from dichloromethane–hexane.

2.3.1. Carbonylation of compound 1a According to the general procedure, the carbonylation of 1a was carried out to give 12-phenylspiro[isoindoline-3,4%-oxolane]-1,11-dione (2a) and furan-2(5H)one (3a). 2a: colorless crystals, 34% isolated yield; m.p. 191°C. IR (KBr): 3369 (nNH), 1770 (nCOO), 1695 (nCON) cm − 1; 1 H NMR (CDCl3): 7.79 (d, 1H, J =7.6 Hz), 7.74 (t, 1H, J =7.1 Hz), 7.67 (d, 1H, J =7.6 Hz), 7.58 (t, 1H, J= 7.1 Hz), 7.30–7.23 (m, 3H), 6.94 (dd, 2H, J =7.8,

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1.5 Hz), 6.50 (s, 1H, NH), 4.69 (d, 1H, J= 10.0 Hz, CH2), 4.52(d, 1H, J=10.0 Hz, CH2), 4.27 (s, 1H, CHPh); 13C NMR (CDCl3): 173.8, 168.8, 142.5, 133.2, 129.9, 129.8, 129.0, 129.0, 128.7, 128.3, 124.6, 120.9, 74.3, 67.8, 54.7; MS m/z 279 (M+). Anal. Calc. for C17H13NO3: C, 73.10; H, 4.69; N, 5.02. Found: C, 72.98; H, 4.51; N, 5.12%. 3a: colorless crystal, 45% isolated yield; m.p. 176°C. IR (KBr): 1758 (nCOO), 1645 (nCON) cm − 1; 1H NMR (CDCl3): 7.65–7.38 (m, 9H, arom), 6.07 (br, 2H, NH2), 5.34 (br, 1H, CH2), 5.22 (br, 1H, CH2); 13C NMR (CDCl3): 173.8, 170.6, 156.5, 136.2, 131.0, 130.8, 130.7, 130.3, 129.7, 129.1, 128.9, 128.0, 127.7, 126.7, 71.0; MS m/z 279 (M+). Anal. Calc. for C17H13NO3: C, 73.10; H, 4.69; N, 5.02. Found: C, 73.02; H, 4.53; N, 5.01%.

2.3.2. Carbonylation of compound 1b According to the general procedure, the carbonylation of 1b was carried out to give spiro compound 2b and furan-2(5H)-one (3b). The NMR showed 2b to be a diastereomeric mixture, which could not be separated by column chromatography. 2b: colorless crystal, 37% isolated yield; m.p. 164°C. IR (KBr): 3013 (nNH), 1779 (nCOO), 1682 (nCON) cm − 1; 1 H NMR (CDCl3): 7.80 (d, 1H, J= 7.6 Hz, arom), 7.77–7.67 (m, 2H, arom), 7.59 (td, 1H, J=6.9, 1.5 Hz, arom), 7.27–7.13 (m, 3H, arom), 6.86 (d, 2H, J=7.3 Hz, arom), 4.74 (d, 1H, J=10.5 Hz, CH2), 4.35 (d, 1H, J= 10.7 Hz, CH2), 4.26 (s, 1H, CHPh), 2.85 (s, 3H, CH3); 13C NMR (CDCl3): 173.3, 167.2, 142.5, 132.6, 132.4, 129.9, 128.6, 128.5, 128.0, 124.2, 120.8, 72.5, 71.9, 52.8, 26.4; MS m/z 235 (M+). Anal. Calc. for C18H15NO3: C, 73.70; H, 5.15; N, 4.78. Found: C, 73.47; H, 4.89; N, 4.50%. 2b%: 1H NMR (CDCl3): 7.69–7.67 (m, 1H, arom), 7.38–7.34 (m, 2H, arom), 7.17–7.15 (m, 3H, arom), 7.00–6.98 (m, 1H, arom), 6.93–6.90 (m, 2H, arom), 4.51 (d, 1H, J= 10.4 Hz, CH2), 4.33 (d, 1H, J =10.5 Hz, CH2), 4.48 (s, 1H, CHPh), 3.18 (s, 3H, CH3). 3b: colorless crystal, 58% isolated yield; m.p. 173°C. IR (KBr): 3367, 1732, 1651 cm − 1; 1H NMR (CDCl3): 7.62 (d, 1H, J= 8.1 Hz), 7.46–7.33 (m, 4H), 7.31–7.24 (m, 3H), 7.15 (d, 1H, J=7.6 Hz), 6.26 (br, 1H, NHCH3), 5.30 (br, 1H, CH2), 5.23 (br, 1H, CH2), 2.82 (d, 3H, J= 4.9 Hz, CH3); 13C NMR (CDCl3): 173.8, 169.4, 137,4, 134.9, 130.7, 130.6, 130.5, 130.4, 129.5, 129.0, 128.9, 127.7, 127.6, 126.7, 71.0, 26.7; MS m/z 235 (M+). Anal. Calc. for C18H15NO3: C, 73.70; H, 5.15; N, 4.78. Found: C, 73.88; H, 5.27; N, 4.99%. 2.3.3. Carbonylation of compound 1c According to the general procedure, the carbonylation of 1c was carried out to give spiro compound 2c and furan-2(5H)-one (3c). Since 2c and 3c could not be separated, their yields were determined by a 1H NMR spectrum.

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2c: 25% yield. 1H NMR (CDCl3): 7.99 – 7.70 (m, 14H, arom), 4.80 (d, 1H, J = 11.0 Hz, CH2), 4.88 (d, 1H, J =10.6 Hz, CH2), 4.56 (s, 1H, CHPh). 2c%: 1H NMR (CDCl3): 7.99 – 7.70 (m, 14H, arom), 4.73 (d, 1H, J =9.3 Hz, CH2), 4.59 (d, 1H, J =9.5 Hz, CH2), 4.27 (s, 1H, CHPh). 3c: 65% yield. 1H NMR (CDCl3): 8.05 (br, 1H, NHPh), 7.77–7.47 (m, 14H, arom), 5.30 (br, 1H, CH2), 5.10 (br, 1H, CH2).

2.3.4. Carbonylation of compound 1d According to the general procedure, the carbonylation of 1d was carried out to give furan-2(5H)-ones (3d and 4d) as colorless crystals, which could not be separated, and their yields were determined by a 1H NMR spectrum. 3d: 47% yield. IR (KBr): 3485, 2933, 1748, 1622 cm − 1; 1H NMR (CDCl3): 7.48 – 7.24 (m, 8H, arom), 7.16 (d, 1H, J= 7.3 Hz), 5.22 (s, 2H, CH2), 3.02 (s, 3H, CH3), 3.01 (s, 3H, CH3); MS m/z 307 (M+). 4d: 47% yield. 1H NMR (CDCl3): 7.49 – 7.24 (m, 9H, arom), 5.26 (s, 2H, CH2), 2.86 (s, 3H, CH3), 2.29 (s, 3H, CH3). 2.3.5. Carbonylation of compound 1e According to the general procedure, the carbonylation of 1e was carried out to give spiro compound 2e and furan-2(5H)-one (3e). 2e: colorless crystal, 33% isolated yield; m.p. 187°C. IR (KBr): 3192, 1792, 1696 cm − 1; 1H NMR (CDCl3): 7.79 (d, 1H, J = 7.6 Hz), 7.74 (t, 1H, J =7.6 Hz), 7.65 (d, 1H, J = 7.5 Hz), 7.58 (t, 1H, J = 7.6 Hz), 6.85 (d, 2H, J = 9.9 Hz), 6.76 (d, 2H, J = 9.6 Hz), 6.39 (br, 1H), 4.68 (d, 1H, J= 9.8 Hz), 4.51 (d, 1H, J =9.8 Hz), 4.24 (s, 1H), 3.74 (s, 3H, OCH3); 13C NMR (CDCl3): 174.0, 168.9, 159.7, 144.8, 133.2, 131.3, 130.2, 129.9, 124.6, 121.6, 120.9, 114.5, 74.2, 67.9, 55.2, 54.2; MS m/z 309 (M+). Anal. Calc. for C18H15NO4: C, 69.89; H, 4.89; N, 4.53. Found: C, 69.72; H, 4.87; N, 4.37%. 3e: colorless crystal, 55% isolated yield; m.p. 181°C. IR (KBr): 3364, 1726, 1674 cm − 1; 1H NMR (CDCl3): 7.73 –7.70 (m, 2H), 7.49 – 7.43 (m, 2H), 7.21 – 7.16 (m, 3H), 6.79 (d, 2H, J=8.8 Hz), 6.27 (br, 1H, NH2), 5.70 (br, 1H, NH2), 5.34 (br, 1H, CH2), 5.19 (br, 1H, CH2), 3.82 (s, 3H, OCH3); 13C NMR (CDCl3): 174.3, 170.7, 161.6, 156.5, 136.5, 131.0, 130.8, 129.8, 129.4, 129.0, 128.2, 124.2, 122.6, 114.4, 70.9, 55.3; MS m/z 309 (M+). Anal. Calc. for C18H15NO4: C, 69.89; H, 4.89; N, 4.53. Found: C, 69.68; H, 4.71; N, 4.45%. 2.3.6. Carbonylation of compound 1f According to the general procedure, the carbonylation of 1f was carried out to give spiro compound 2f and furan-2(5H)-one (3f) as colorless crystals. 2f and 3f could not be separated and their yields were determined by a 1H NMR spectrum.

2f: 27% yield. IR (KBr): 3374, 3189, 2233, 1746, 1674 cm − 1; 1H-NMR (CDCl3): 7.73 (d, 1H, J=7.3 Hz), 7.59 (d, 2H, J= 8.8 Hz), 7.54–7.43 (m, 2H), 7.37(d, 2H, J=8.5 Hz), 7.02 (d, 1H, J=8.3 Hz), 6.50 (br, 1H), 4.79(d, 1H, J=9.7 Hz), 4.53 (d, 1H, J= 9.7 Hz), 4.40 (s, 1H); MS m/z 304 (M+). 3f: 40% yield. 1H-NMR (CDCl3): 7.72 (d, 2H, J=7.3 Hz), 7.59 (d, 2H, J= 7.6 Hz), 7.52–7.43 (m, 2H), 7.37 (d, 1H, J= 8.1 Hz), 7.11 (d, 2H, J= 7.6 Hz), 6.09 (br, 1H, NH2), 5.59 (br, 1H, NH2), 5.36 (br, 1H, CH2), 5.18 (br, 1H, CH2).

2.3.7. Carbonylation of compound 1h According to the general procedure, the carbonylation of 1h was carried out to give spiro compound 2h and furan-2(5H)-ones (3h and 4h). In this case, 37% of 1h was recovered. 2h: colorless crystal, 21% isolated yield; m.p. 194°C. IR (KBr): 1770, 1695 cm − 1; 1H NMR (CDCl3): 7.91– 7.72 (m, 11H), 5.69 (br, 1H, NH), 4.90 (s, 1H), 4.75 (d, 1H, J= 10.0 Hz, CH2), 4.53 (d, 1H, J= 10.0 Hz, CH2); 13 C NMR (CDCl3): 168.8, 145.1, 141.8, 137.9, 133.5, 132.3, 131.4, 129.9, 129.4, 128.7, 128.5, 126.9, 126.5, 126.3, 125.9, 125.4, 124.9, 124.6, 123.9, 122.6, 120.9, 68.7; MS m/z 329 (M+). Anal. Calc. for C21H15NO3: C, 76.58; H, 4.59; N, 4.25. Found: C, 76.66; H, 4.77; N, 4.24%. 3h: colorless crystal, 40% isolated yield; m.p. 222°C. IR (KBr): 1755, 1650 cm − 1; 1H NMR (CDCl3): 8.08 (d, 1H, J= 8.3 Hz), 7.88–7.86 (m, 1H), 7.80 (d, 1H, J = 8.1 Hz), 7.55 (d, 1H, J= 7.8 Hz), 7.49–7.48 (m, 2H), 7.46–7.34 (m, 2H), 7.21(t, 1H, J=7.6 Hz), 7.07(t, 1H, J= 7.6 Hz), 7.89 (d, 1H, J=7.1 Hz), 6.03 (br, 1H, NH2), 5.56 (br, 1H, NH2), 5.25 (s, 2H, CH2); 13C NMR (CDCl3): 172.8, 171.00, 157.1, 134.9, 133.5, 130.7, 130.5, 130.1, 130.1, 129.8, 129.0, 128.6, 128.2, 127.3, 127.0, 126.5, 126.3, 125.5, 125.0, 73.0; MS m/z 329 (M+). 4h: colorless crystal, 16% isolated yield; m.p. 215°C. IR (KBr): 1755, 1651 cm − 1; 1H NMR (CDCl3): 7.77– 7.71 (m, 3H), 7.7.42–7.7.21 (m, 6H), 7.10 (d, 2H, J= 7.6 Hz), 5.40–5.16 (m, 4H, NH2 + CH2); 13C NMR (CDCl3): 173.4, 169.5, 162.6, 133.9, 133.6, 131.5, 131.3, 129.8, 129.7, 129.5, 128.9, 128.5, 128.1, 127.62, 127.5, 126.6, 126.5, 125.6, 125.6, 72.9; MS m/z 329 (M+). Anal. Calc. for C21H15NO3: C, 76.58; H, 4.59; N, 4.25. Found: C, 76.56; H, 4.75; N, 4.05%. 2.4. Treatment of 4h with Et3N A solution of 4h (0.16 mmol) and Et3N (150 mg, 1.4 mmol) in 1,4-dioxane (15 mmol) was placed in a 100 ml stainless steel autoclave and stirred at 80°C for 10 days. After removal of the solvent from the reaction mixture under reduced pressure, 2h was obtained in 98% yield (determined by a 1H NMR spectrum).

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2.5. Crystallographic data for 2a, 3a and 3h The molecular structures of compounds 2a, 3a and 3h have been determined by X-ray crystallographic analyses. Their crystal parameters are shown in Table 1.

3. Results and discussion

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the cyclic carbonylation of the carboncarbon triple bond took place involving incorporation of the carbonyl groups of formyl as well as alkoxycarbonyl substituents. These two reactions were performed under the same reaction conditions except for the reaction temperature, but they resulted in the formation of different products, tricyclic lactone and tetracyclic lactone, respectively, by different reaction routes [5e]. Based on these experimental results, we examined the carbonylation of 2-ethynylbenzamide derivative (1), which also has a carbonyl group adjacent to the carboncarbon triple bond, and found that the carbonylation of 2phenylethynylbenzamide (1a) gives an unexpected spiro compound 2a along with 2(5H)-furanone (3a) (Eq. (3)).

(2) As described above, we have developed several new types of cyclic carbonylation reactions of alkynes bearing a functional group adjacent to the acetylenic bond which are catalyzed by Rh6(CO)16 under WGSR conditions. In these reactions, the neighboring group takes part in the carbonylation of the acetylenic bond resulting in the formation of some novel lactone and lactam derivatives. Among them, two types of reactions shown in Eq. (2) are of special interest, since in both reactions

(3) Alkynes with an amide group were prepared by a coupling reaction between the terminal acetylenes and aryl halides using a CuIPd(PPh3)2Cl2 catalyst [7]. Carbonylation of alkyne 1 is performed in the presence of

Table 1 Crystal parameters and refinements for 2a, 3a and 3h

Empirical formula Formula weight Crystal color, habit Crystal dimensions (mm) Crystal system Lattice type No. of reflection used for unit cell determination (2u range) (°) V scan peak width at half-height (°) Lattice parameters a (A, ) b (A, ) c (A, ) b (°) V (A, 3) Space group Z value Dcalc (g cm−3) F(000) m (Mo Ka) (cm−1) Residuals: R, Rw

2a

3a

3h

C17H13NO3 279.29 colorless, prismatic 0.75×0.40×0.35 monoclinic primitive 25 (39.6–40.0) 0.21

C17H13NO3 279.29 colorless, prismatic 0.60×0.40×0.25 monoclinic primitive 24 (39.3–39.8) 0.20

C21H15NO3 329.35 colorless, prismatic 0.50×0.50×0.25 monoclinic primitive 25 (29.1–30.0) 0.23

9.29(6) 12.02(7) 12.39(9) 96.4 1374(13) P21/n (no. 14) 4 1.349 584.00 0.93 0.050, 0.049

10.157(1) 17.892(2) 7.618(1) 93.40(1) 1381.9(3) P21/c (no. 14) 4 1.342 584.00 0.93 0.051, 0.052

8.029(3) 19.622(7) 10.200(2) 97.16(2) 1594.4(9) P21/n (no. 14) 4 1.372 688.00 0.92 0.062, 0.110

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Fig. 1. An ORTEP drawing of 2a. Selective bond distances (A, ) and angles (°): O(1)C(3), 1.205(2); O(2)C(3), 1.357(5); O(2)C(4), 1.458(2); O(3)C(5), 1.223(3); N(1)C(1), 1.457(3); N(1)C(5), 1.365(4); C(1)C(2), 1.550(3); C(1)C(4), 1.53(1); C(1)C(7), 1.515(3); C(2)C(3), 1.514(5); C(2)C(12), 1.504(9); C(3)O(2)C(4), 109.9(2); C(1)N(1)C(5), 113.5(2); N(1)C(5)C(6), 106.4(2); N(1)C(1)C(7), 101.8(2), C(2)C(1)C(4), 100.2(2); C(1)C(2)C(3), 102.0(2); O(1)C(3)O(2), 120.1(2); O(2)C(4)C(1), 104.6(2).

a rhodium catalyst under WGSR conditions. Thus, 2-phenylethynylbenzamide was treated with carbon monoxide in the presence of a Rh6(CO)16 catalyst, NEt3, and H2O in 1,4-dioxane at 80°C for 3 days. After removal of the solvent from the reaction mixture, TLC analysis of the residue showed the formation of two kinds of products. Separation by column chromatography on silica gel and recrystallization from dichloromethane –hexane gave a new compound 2a and furanone 3a in 34 and 45% yields, respectively. Furanone 3a was identified by IR, mass, 1H and 13C NMR as well as by comparison with the spectral data of furanone derivatives [4]. The structure of 2a having the same mass number as 3a was inferred from the analytical and spectral data. In contrast to 3a, complicated peaks were observed in the 1H NMR spectrum of 2a, suggesting that 2a has a different molecular structure from that of 3a. The structure of 2a was established finally by an X-ray crystallographic analysis, indicating that it is a tricyclic hetero compound, 12phenylspiro[isoindoline-3,4%-oxolane]-1,11-dione. The ORTEP drawing of 2a is illustrated in Fig. 1 with important bond distances and angles. The structure showed that 2a consists of one six-membered ring and two five-membered rings, and that the two five-membered rings give a spiro structure where a new CN bond was formed by the nitrogen of the amide group and one carbon of the triple bond of substrate 1a. The

five-membered lactone ring is not planar and forms a very strained structure. By a close inspection of the structure of 2a, we could consider that, in the reaction of 1a, the cyclic carbonylation of the CC triple bond took place to give two furanones which are a pair of structural isomers and then one of the furanones might be converted to 2a by addition of the NH of the amide group to the double bond of the furanone. In order to know the configuration of 3a, an X-ray crystallographic analysis for 3a was also carried out. Fig. 2 depicts the ORTEP drawing, which reveals that 3a adopts a configuration of one possible isomer of furanones in which the amide group is on the CO side of the furanone ring. No other furanone was obtained in this reaction. The reaction of 1a for a shorter reaction time of 24 h gave 2a and 3a with recovered 1a, but the furanone which is expected to be a structural isomer of 3a was not detected. In comparison with the reaction of 1a, the results obtained from carbonylations of alkynes 1b–d are summarized in Table 2. The reactions of 2-phenylethynylbenzamide derivatives 1b and 1c gave the corresponding spiro products 2b and 2c in 37 and 25% yields, respectively. Both reactions were accompanied by the formation of furanones 3b and 3c, in which the amide group is also on the CO side of the furanone ring. On the other hand, in the reaction of N,Ndimethyl-2-phenylethynylbenzamide (1d), only two

S.-W. Zhang et al. / Inorganica Chimica Acta 296 (1999) 195–203

furanones 3d and 4d were obtained in a total yield of 94%. No further cyclization occurred, that is, the amide group remained intact. It is noteworthy that the reaction of 1d gave only two isomers of furanones 3d and 4d but not a spiro compound, and a furanone derivative like 4d having an amide group on the opposite side to the furanone carbonyl group was not detected in the carbonylation of 1a – c. These results suggest that spiro compounds would be formed via a furanone intermediate which has a structure like 4d, but it should have a NH bond at the amide group. As we previously reported [4], in the synthesis of furan-2(5H)-ones the selectivity of products 3 and 4 was affected by the electronic property of the substituents X and Y on alkynes XC6H4CCC6H4Y. Since selective formation of furanone 4 would improve the selectivity for spiro compound 2, we performed the reactions of 2-phenylethynylbenzamide derivatives 1e and 1f with an electron-donating or -withdrawing substituent on the phenyl group under the same reaction conditions. The carbonylations gave the corresponding spiro derivatives 2e in 33% and 2f in 27% yield along with furanones 3e and 3f (Table 3). However, as compared with the reaction of 1a, no improvement was observed for the selectivity of spiro product 2.

201

Table 2

Alkyne

a

R%

H Me Ph Me

1a 1b 1c 1d

b

R

H H H Me

Yield (%) 2

3

4

34 a 37 a 25 b –

45 a 58 a 65 b 47 b

– – – 47 b

Isolated yield. Determined by 1H NMR.

The steric effect was then examined. Bulky 2-mesityl ethynylbenzamide (1g) did not undergo carbonylation under the same reaction conditions, and 1g was completely recovered. The carbonylation of 2-naphthylethynylbenzamide (1h) proceeded very slowly to afford three kinds of products, spiro compound 2h in 21% yield (based on 63% conversion of 1h) and two isomers of furanones 3h (40% yield) and 4h (16% yield), accompanied by recovered 1h (37%). The structures of Table 3

(4)

Alkyne

H OMe CN

1a 1e 1f

(5)

R

a b

Isolated yield. Determined by 1H NMR.

Yield (%) 2

3

34 a 33 a 27 b

45 a 55 a 40 b

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Fig. 2. An ORTEP drawing of 3a. Selective bond distances (A, ) and angles (°): O(1)C(3), 1.443(3); O(1)C(4), 1.358(3); O(2)C(4), 1.207(3); C(1)C(2), 1.353(3); C(1)C(4), 1.470(4); C(2)C(3), 1.489(4); C(2)C(12), 1.466(4); C(1)C(2)C(12), 129.7(2); C(2)C(1)C(7), 130.8(2); C(1)C(2)C(3), 108.3(2); C(2)C(1)C(4), 108.1(2); O(1)C(4)O(2), 121.5(2).

2h, 3h and 4h were determined by analytical and spectral data, and finally by an X-ray crystallographic analysis for 3h (Fig. 3). We could obtain, fortunately, furanone 4h which is a structural isomer of 3h and a postulated precursor leading to spiro product 2h. In

order to clear the mechanism, we treated 4h under the same reaction conditions as the carbonylation in the absence of the rhodium catalyst, and confirmed the quantitative conversion of 4h to spiro compound 2h (Eqs. (4) and (5)).

Fig. 3. An ORTEP drawing of 3h. Selective bond distances (A, ) and angles (°): O(1)C(3), 1.359(5); O(1)C(4), 1.427(4); O(2)C(3), 1.201(4); C(1)C(2), 1.335(5); C(1)C(4), 1.507(5); C(2)C(3), 1.479(4); C(2)C(5), 1.472(5); C(1)C(12), 1.471(4); C(1)C(2)C(5), 129.8(3); C(2)C(1)C(12), 129.1(3); C(1)C(2)C(3), 108.0(3); C(2)C(1)C(4), 108.7(3); O(1)C(4)O(2), 122.6(3).

S.-W. Zhang et al. / Inorganica Chimica Acta 296 (1999) 195–203

203

Scheme 1.

Based on the previously proposed mechanism for the carbonylation of alkynes giving 2(5H)-furanones [4], a possible mechanism of the formation of spiro compound 2 is shown in Scheme 1. A rhodium complex formed by the coordination of alkyne undergoes insertion of two molecules of CO, followed by the attack of H+ and OH−, yielding two precursors, A and B. Elimination of [Rh] from precursors A and B affords furanones 3 and 4, respectively. Since furanone 4 has a structure where the amide group is located nearby to interact with the b-carbon of a,b-unsaturated lactone, nucleophilic attack of the amide nitrogen to the furanone ring would occur to give 2. The addition of an NH group to a,b-unsaturated ketone is already known [8].

4. Conclusions The carbonylation of 2-phenylethynylbenzamide derivatives catalyzed by Rh6(CO)16 under water–gas shift reaction conditions gave spiro compound 2 and 2-(5H)-furanone (3), the former being formed by the participation of the amide group adjacent to the carboncarbon triple bond in the cyclization. The formation of spiro compounds is interpreted by the intramolecular transformation of furanone 4 which involves a nucleophilic attack of an amide nitrogen to the furanone moiety.

Acknowledgements This work is partially supported by a grant-in-aid from the Ministry of Education, Science, Sports, and

.

Culture, Japan, for Encouragement of Young Scientists (No. 10750625). We are grateful to the Materials Analysis Center, ISIR, Osaka University, for the elemental analyses.

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