Synlett 2006(2): 231-234  
DOI: 10.1055/s-2005-923590
LETTER
© Georg Thieme Verlag Stuttgart · New York

Chemo- and Regioselective Addition of Carboxylic Acid to the Alkylthio-­Activated Enyne Triple Bond in the Absence of Catalysts

Yu-Long Zhao*, Qun Liu*, Yan-Feng Zhang, Shao-Guang Sun, Yuan-Na Li
Department of Chemistry, Northeast Normal University, Changchun, 130024, P. R. of China
e-Mail: zhaoyl351@nenu.edu.cn; e-Mail: liuqun@nenu.edu.cn;
Further Information

Publication History

Received 13 October 2005
Publication Date:
23 December 2005 (online)

Abstract

A series of methyl 3-acetoxy-2-(1,3-dithiolane-2-ylidene)but-3-enoate derivatives has been synthesized by the chemo- and regioselective addition of carboxylic acids to the alkyl­thio-activated terminal alkynes in moderate to high yields in the ­absence of catalysts.

17

Preparation of 2b3 as a Typical Procedure. The reaction of Boc-glycine (1.2 mmol, 210 mg) and alkyne 1b (1.0 mmol, 200 mg) was carried out in MeCN under reflux temperature for 30 h. After alkyne 1b was consumed (monitored by TLC), the reaction mixture was poured into cold sat. NaHCO3 solution (50 mL) and extracted with Et2O (3 × 10 mL). The combined organic extracts were dried over anhyd MgSO4, filtered and concentrated under reduced pressure to yield the crude product, which was purified by chromatography over silica gel column using Et2O-hexane (1:3) as eluent to give 300 mg (80%) of 2b3 as a white crystalline solid.
Methyl 3-[2-( tert -Butoxycarbonyl)acetoxy]-2-(1,3-dithian-2-ylidene)but-3-enoate ( 2b3).
Mp 99-101 °C. 1H NMR (400 MHz, CDCl3): δ = 1.45 (s, 9 H), 3.34-3.37 (m, 2 H), 3.47-3.50 (m, 2 H), 3.76 (s, 3 H), 4.00 (s, 2 H), 5.01 (br s, 1 H), 5.14 (d, J = 2.0 Hz, 1 H), 5.35 (d, J = 2.0 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ = 28.22 (3 C), 36.38, 39.38, 42.37, 51.96, 79.94, 108.63, 111.62, 149.42, 155.50, 165.03, 168.05, 169.35. IR (KBr): 3376, 2980, 2937, 1762, 1716, 1690, 1518, 1368, 1270, 1150, 1001 cm-1. MS (EI): m/z = 398 [M + 23]+. Anal. Calcd for C15H21O6S2N: C, 47.98; H, 5.64; N, 3.73. Found: C, 47.82; H, 5.60; N, 3.62.
3-(1,3-Dithiolan-2-ylidene)-4-methoxy-4-oxobut-1-en-2-ylbenzoate ( 2b2).
Colorless liquid. 1H NMR (500 MHz, CDCl3): δ = 3.36-3.39 (m, 2 H), 3.47-3.50 (m, 2 H), 3.73 (s, 3 H), 5.21 (d, J = 1.5 Hz, 1 H), 5.45 (d, J = 1.5 Hz, 1 H), 7.44 (t, J = 7.0 Hz, 2 H), 7.56 (q, J = 7.0 Hz, 1 H), 8.06 (q, J = 7.0 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 36.75, 39.64, 52.29, 108.88, 112.42, 128.70 (2 C), 129.91, 130.29 (2 C), 133.58, 150.34, 164.50, 165.66, 169.37. IR (KBr): 3065, 2944, 1734, 1695, 1597, 1499, 1248, 1214, 1088, 999, 886 cm-1. MS (EI): m/z = 323 [M + 1]+. Anal. Calcd for C15H14O4S2: C, 55.88; H, 4.38. Found: C, 55.81; H, 4.33.
3-(1,3-Dithiolan-2-ylidene)-4-methoxy-4-oxobut-1-en-2-yl-4-nitrobenzoate ( 2b4).
White crystal; mp 146-148 °C. 1H NMR (500 MHz, CDCl3): δ = 3.40 (t, J = 6.0 Hz, 2 H), 3.51 (t, J = 6.0 Hz, 2 H), 3.73 (s, 3 H), 5.27 (s, 1 H), 5.49 (s, 1 H), 8.24 (d, J = 9.0 Hz, 2 H), 8.30 (d, J = 9.0 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 36.80, 39.71, 52.29, 109.33, 111.83, 123.87 (2 C), 131.36 (2 C), 135.40, 150.09, 150.95, 162.60, 165.41, 170.13. IR (KBr): 3105, 2957, 1738, 1688, 1526, 1281, 1217, 1099 cm-1. MS (EI): m/z 368 [M + 1]+. Anal. Calcd for C15H13O6NS2: C, 49.04; H, 3.57; N, 3.81. Found: C, 49.00; H, 3.68; N, 3.69.
3-(1,3-Dithiolan-2-ylidene)-4-methoxy-4-oxobut-1-en-2-yl-4-methoxybenzoate ( 2b5). White crystal; mp 124-126 °C. 1H NMR (500 MHz, CDCl3): δ = 3.38 (t, J = 6.5 Hz, 2 H), 3.50 (t, J = 6.5 Hz, 2 H), 3.74 (s, 3 H), 3.88 (s, 3 H), 5.20 (s, 1 H), 5.44 (s, 1 H), 6.93 (d, J = 8.5 Hz, 2 H), 8.03 (d, J = 8.5 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 36.72, 39.58, 52.21, 55.69, 108.55, 112.72, 113.93 (2 C), 122.28, 132.39 (2 C), 150.39, 163.89, 164.18, 165.69, 168.94. IR (KBr): 2953, 2929, 1717, 1683, 1607, 1499, 1286, 1257, 1223, 1166, 1082, 997 cm-1. MS (EI): m/z = 353 [M + 1]+. Anal. Calcd for C16H16O5S2: C, 54.53; H, 4.58. Found: C, 54.48; H, 4.50.
Methyl 3-(2-Chloroacetoxy)-2-(1,3-dithiolan-2-ylidene)but-3-enoate ( 2b6). White crystal; mp 74-76 °C. 1H NMR (500 MHz, CDCl3): δ = 3.37 (t, J = 6.5 Hz, 2 H), 3.51 (t, J = 6.5 Hz, 2 H), 3.76 (s, 3 H), 4.14 (s, 2 H), 5.19 (d, J = 1.0 Hz, 1 H), 5.39 (d, J = 1.0 Hz, 1 H). 13C NMR (125 MHz, CDCl3): δ = 36.69, 39.74, 41.19, 52.26, 109.26, 111.55, 149.85, 165.07, 165.27, 170.21. IR (KBr): 3020, 2950, 1766, 1687, 1633, 1507, 1439, 1267, 1222, 1159, 1082, 961 cm-1. MS (EI): m/z = 296 [M + 1]+. Anal. Calcd for C10H11ClO4S2: C, 40.75; H, 3.76. Found: C, 40.86; H, 3.81.
3-(1,3-Dithian-2-ylidene)-4-methoxy-4-oxobut-1-en-2-yl Benzoate ( 2a2). Colorless liquid. 1H NMR (500 MHz, CDCl3): δ = 2.18-2.21 (m, 2 H), 2.96-3.02 (m, 4 H), 3.71 (s, 3 H), 5.10 (d, J = 2.0 Hz, 1 H), 5.55 (d, J = 2.0 Hz, 1 H), 7.45 (q, J = 7.5 Hz, 2 H), 7.56 (d, J = 7.5 Hz, 1 H), 8.05 (quint, J = 7.5 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 23.91, 29.60, 30.06, 52.19, 109.89, 121.13, 128.70, 128.75, 129.93, 130.27, 130.43, 133.59, 147.95, 164.44, 164.64, 164.88. IR (KBr): 2989, 1736, 1694, 1500, 1453, 1248, 1215, 1084, 885 cm-1. MS (EI): m/z = 337 [M + 1]+. Anal. Calcd for C16H16O4S2: C, 57.12; H, 4.79. Found: C, 57.24; H, 4.89.
Methyl 3-[2-( tert -Butoxycarbonyl)acetoxy]-2-(1,3-dithian-2-ylidene)but-3-enoate ( 2a3). White crystal; mp 104-106 °C. 1H NMR (400 MHz, CDCl3): δ = 1.45 (s, 9 H), 2.17-2.21 (m, 2 H), 2.95-3.00 (m, 4 H), 3.75 (s, 3 H), 3.97 (s, 2 H), 4.97 (br s, 1 H), 5.02 (d, J = 2.0 Hz, 1 H), 5.45 (d, J = 2.0 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ = 23.52, 28.25 (3 C), 29.25, 29.68, 42.47, 51.83, 79.98, 109.51, 120.32, 147.18, 155.49, 164.30, 164.49, 167.99. IR (KBr): 3380, 2933, 1779, 1695, 1513, 1455, 1426, 1223, 1135, 1084 cm-1. MS (EI): m/z = 412 [M + 23]+. Anal. Calcd for C16H23O6S2N: C, 49.34; H, 5.95; N, 3.60. Found; C, 49.49; H, 6.06; N, 3.67.
3-(1,3-Dithian-2-ylidene)-4-methoxy-4-oxobut-1-en-2-yl-4-nitrobenzoate ( 2a4). White crystal; mp 144-146 °C. 1H NMR (500 MHz, CDCl3): δ = 2.17-2.22 (m, 2 H), 2.99-3.02 (m, 4 H), 3.72 (s, 3 H), 5.15 (s, 1 H), 5.58 (s, 1 H), 8.22 (d, J = 7.5 Hz, 2 H), 8.29 (d, J = 7.5 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 23.84, 29.62, 30.06, 52.14, 110.23, 120.46, 123.86 (2 C), 131.33 (2 C), 135.44, 147.80, 150.94, 162.53 (2 C), 164.66. IR (KBr): 3446, 1740, 1695, 1527, 1457, 1277, 1248, 1097 cm-1. MS (EI): m/z 382 [M + 1]+. Anal. Calcd for C16H15NO6S2: C, 50.38; H, 3.96; N, 3.67. Found: C, 50.44; H, 3.88; N, 3.72.
3-(1,3-Dithian-2-ylidene)-4-methoxy-4-oxobut-1-en-2-yl-4-methoxybenzoate(2a5). White crystal; mp 122-123 °C. 1H NMR (500 MHz, CDCl3): δ = 2.15-2.19 (m, 2 H), 2.94-3.00 (m, 4 H), 3.69 (s, 3 H), 3.85 (s, 3 H), 5.06 (s, 1 H), 5.51 (s, 1 H), 6.90 (d, J = 7.5 Hz, 2 H), 7.99 (d, J = 7.5 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 23.84, 29.48, 29.93, 52.00, 55.62, 109.36, 113.87 (2 C), 121.42, 122.26, 132.28 (2 C), 147.97, 163.70, 163.83, 164.03, 164.84. IR (KBr): 893, 1032, 1165, 1213, 1263, 1457, 1494, 1605, 1694, 1719, 2948 cm-1. MS (EI): m/z = 367 [M + 1]+. Anal. Calcd for C17H18O5S2: C, 55.72; H, 4.95. Found: C, 55.81; H, 5.02.

18

General Procedures for the Preparation of Compounds 2a1 and 2b1.
To a solution of alkyne 1 (2.00 mmol) in AcOH (10 mL) was stirred at r.t. for 4 h. After alkyne 1 was consumed (monitored by TLC), the reaction mixture was poured slowly into cold sat. NaHCO3 solution (50 mL), extracted with Et2O (3 × 10 mL). The combined organic extracts were washed with H2O (2 × 10 mL), dried over anhyd MgSO4. The solvent was removed under reduced pressure, and the residue was purified by silica gel chromatography using Et2O-hexane (1:8) as eluent to give the corresponding product 2a1 or 2b1.
Methyl 3-Acetoxy-2-(1,3-dithiolan-2-ylidene)but-3-enoate ( 2b1). Colorless liquid. 1H NMR (500 MHz, CDCl3): δ = 2.12 (s, 3 H), 3.33-3.36 (m, 2 H), 3.47-3.49 (m, 2 H), 3.76 (s, 3 H), 5.12 (d, J = 1.5 Hz, 1 H), 5.29 (d, J = 1.5 Hz, 1 H). 13C NMR (125 MHz, CDCl3): δ = 21.46, 36.73, 39.70, 52.30, 108.71, 112.50, 149.91, 165.53, 168.63, 169.03. IR (KBr): 2949, 1757, 1685, 1507, 1271, 1197, 1085, 1018 cm-1. MS (EI): m/z 261 [M + 1]+. Anal. Calcd for C10H12O4S2: C, 46.14; H, 4.65. Found: C, 46.27; H, 4.57.
Methyl 3-Acetoxy-2-(1,3-dithian-2-ylidene)but-3-enoate ( 2a1).
Colorless liquid. 1H NMR (500 MHz, CDCl3): δ = 2.11 (s, 3 H), 2.17-2.20 (m, 2 H), 2.95-2.99 (m, 4 H), 3.74 (s, 3 H), 5.00 (s, 1 H), 5.38 (s, 1 H). 13C NMR (125 MHz, CDCl3): δ = 21.54, 23.90, 29.57, 30.02, 52.15, 109.61, 121.15, 147.59, 164.04, 164.73, 168.56. IR (KBr): 2927, 1756, 1691, 1509, 1427, 1373, 1228, 1199, 1083 cm-1. MS (EI): m/z = 275 [M + 1]+. Anal. Calcd for C11H14O4S2: C, 48.16; H, 5.14. Found: C, 48.10; H, 5.21.