Issue in Honor of Prof. Cheng-Ye Yuan ARKIVOC 2004 (ix) 15-18
Experimental Section
General Procedures. All reactions were carried out in Schlenk tubes under nitrogen atmosphere. 1H NMR spectra were measured at 400 MHz in CDCl3 with TMS as internal standard. Mass spectra were obtained by EI method. IR spectra were obtained by use of neat capillary cells (liquid samples) or KBr disks (solid samples). Melting points were uncorrected.
General procedure for the stereoselective synthesis of (E)-a-halo-a, ß-unsaturated nitriles 3 by the tandem reaction of umpolung ylides 2 A mixture of a-hypervalent iodine functionalized phosphonium ylides 2 (2 mmol), tetrakisalkylammonium halide (2 mmol), and aldehyde (2 mmol) in CH2Cl2 (20 mL) was stirred at room temperature for 18-48 h. After the reaction was complete, the organic phase was washed with water (10 mL× 2) and dried over magnesium sulfate. After evaporation of the solvent, the
crude product was purified by preparative TLC (silica gel, hexane-ethyl acetate as eluent) to give a-halo-a, ß-unsaturated nitriles 3. (E)-2-Chloro-3-(p-nitrophenyl)-propenenitrile (3a). mp 82-84 oC(lit.4 mp 85-86 oC). 1H NMR
(400MHz, CDCl3) d ppm 7.45 (s, 1H), 7.86 (d, J = 8.6 Hz, 2H), 8.32 (d, J = 8.8 Hz, 2H). IR . (cm-1): 3110, 2224, 1593, 1518, 1347, 1012, 903, 817. MS (m/z):210 (M+2, 33.3), 208 (M, 99.1), 178 (53.4), 150 (81.9), 127 (96.2), 126 (100.0), 100 (58.2), 99 (52.0), 75 (58.7), 50 (77.9). (E)-2-Chloro-3-(p-chlorophenyl)-propenenitrile (3b). mp 48-50 oC (lit.4 mp 51-52 oC). 1H NMR (400MHz, CDCl3) d ppm 7.31 (s, 1H), 7.43 (d, J = 8.7 Hz, 2H), 7.63 (d, J = 8.7 Hz, 2H). IR . (cm-1): 2926, 2219, 1637, 1591, 1492, 1122, 1014, 830. MS (m/z): 199 (M+2, 55.8), 197 (87.2), 164 (31.4), 162 (100.0), 127 (38.6), 126 (32.5), 75 (36.0), 50 (33.4). (E)-2-Bromo-3-(p-nitrophenyl)-propenenitrile (3c). mp 96-98 oC(lit.4 mp 98-100 oC). 1H NMR (400MHz, CDCl3) d ppm 7.67 (s, 1H), 7.87 (d, J = 8.8 Hz, 2H), 8.31 (d, J = 8.8 Hz, 2H). IR . (cm-1): 3111, 2213, 1585, 1515, 1346, 1110, 999, 917, 862, 799. MS (m/z): 254 (M+2, 41.0), 252 (M, 41.0), 224 (24.0), 222 (25.1), 127 (100.0), 115 (36.0), 100 (40.5), 75 (25.6), 50 (47.8). (E)-2-Bromo-3-(p-chlorophenyl)-propenenitrile (3d). mp 46-48 oC (lit.4 mp 48-50 oC). 1H NMR (400MHz, CDCl3) d ppm 7.42 (d, J =8.5 Hz, 2H), 7.52 (s, 1H), 7.65 (d, J = 8.4 Hz). IR . (cm-1): 3028, 2209, 1589, 1485, 1098, 997, 894, 806. MS (m/z): 243 (M+2, 100.0), 241 (75.4), 208 (30.8), 206 (33.1), 162 (56.9), 127 (82.4), 126 (66.2), 99 (37.7), 75 (63.1), 50 (56.2). (E)-2-Iodo-3-(p-nitrophenyl)-propenenitrile (3e). mp 108-110 oC(lit.5 mp 108-110 oC) . 1H NMR (400MHz, CDCl3) d ppm 7.86 (d, J = 8.8 Hz, 2H), 7.89 (s, 1H), 8.28 (d, J = 8.8 Hz, 2H). IR . (cm-1): 3041, 2212, 1582, 1514, 1348, 1110, 912, 849. MS (m/z): 300 (M, 100.0), 270 (31.0), 127 (96.3), 115(68.1), 100 (46.8), 76(39.6), 50 (69.9). (E)-2-Bromo-3-(p-methoxyphenyl)-propenenitrile (3f). mp 64-66 oC(lit.4 mp 66-67 oC). 1H NMR (400MHz, CDCl3) d ppm 6.97 (d, J = 9.2 Hz, 2H), 7.49 (s, 1H), 7.71 (d, J = 8.8 Hz, 2H). IR . (cm-1): 3034, 2207, 1608, 1589, 1515, 1303, 1264, 1183, 1022, 826. MS (m/z): 139 (M+2, 94.9), 237 (M, 100.0), 224 (20.8), 222 (21.8), 158 (28.7), 115 (38.1), 114 (38.1), 88 (31.8), 77 (20.4), 63 (36.0), 50 (23.7)
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