LETTER
A New Modification of the Bohlmann-Rahtz Pyridine Synthesis
1151
q, J 7.6, CH2), 2.53 (3H, s, Me), 1.19 (3H, t, J 7.6, Me), 0.89
7.30 (5H, m, PhH), 6.94 (1H, s, CH), 4.01 (2H, q, J 7.1, CH2),
2.54 (3H, s, Me), 2.50 (3H, s, Me), 0.90 (3H, t, J 7.1, CH2Me);
δC (100 MHz, CDCl3) 169.5 (C), 159.1 (C), 155.5 (C), 148.9
(C), 139.2 (C), 128.9 (CH), 128.8 (CH), 128.2 (CH), 126.1
(C), 121.6 (CH), 61.7 (CH2), 24.9 (Me), 23.2 (Me), 14.0 (Me);
tert-Butyl 2,6-dimethylpyridine-3-carboxylate 4j (Found
MH+, 208.1337. C12H18NO2 requires 208.1337); νmax (film)
2977, 2930, 2856, 1720, 1592, 1568, 1127, 1083 cm-1; δH (400
MHz; CDCl3) 7.95 (1H, d, J 8.0, 4-PyH), 6.97 (1H, d, J 8.0, 5-
PyH), 2.71 (3H, s, Me), 2.51 (3H, s, Me), 1.53 (9H, s, CMe3);
δC (100 MHz, CDCl3) 166.6 (C), 161.0 (C), 159.1 (C), 139.1
(CH), 124.9 (C), 120.8 (CH), 82.1 (C), 28.6 (Me), 25.2 (Me),
25.0 (Me); tert-Butyl 2,6-dimethyl-4-ethylpyridine-3-
(3H, t, J 7.2, Me), δC (100 MHz, CDCl3) 169.5 (C), 159.4 (C),
156.8 (C), 140.8 (C), 128.8 (CH), 128.7 (CH), 128.7 (CH),
126.5 (C), 121.8 (CH), 61.7 (CH2), 26.6 (CH2), 25.0 (Me),
15.1 (Me), 14.0 (Me); Ethyl 6-methyl-2-phenylpyridine-3-
carboxylate 4f (Found MH+, 242.1181. Calculated for
C15H16NO2 (MH+) 242.1181); νmax (film) 2981, 2926, 1718,
1589, 1137, 1052, 838, 766 cm-1; δH (400 MHz; CDCl3) 7.93
(1H, d, J 8.0, CH), 7.37 (5H, m), 7.10 (1H d, J 8.0, CH), 4.03
(2H, q, J 7.2, CH2), 2.56 (3H, s, Me), 0.94 (3H, t, J 7.2,
CH2Me), δC (100 MHz, CDCl3) 168.6 (C), 161.2 (C), 159.1
(C), 141.0 (C), 138.7 (CH), 129.2 (CH), 128.9 (CH), 128.5
(CH), 124.8 (C), 121.6 (CH), 61.7 (CH2), 27.8 (Me), 14.0
(Me); Ethyl 2-(2-furyl)-6-methyl-4-(trimethylsilyl)pyridine-
3-carboxylate 4g (Found MH+, 304.1370. C16H22NO3Si
requires 304.1369); νmax (film) 2962, 2898, 1727, 1570, 1520,
1165, 1087, 1015, 836, 757 cm-1; δH (400 MHz; CDCl3) 7.49
(1H, s, CH), 7.17 (1H, s, CH), 6.93 (1H, d, J 2, CH), 6.43 (1H,
d, J 2, CH), 4.26 (2H, q, J 7.2, CH2), 2.54 (3H, s, Me), 1.21
(3H, t, J 7.2, Me), 0.26 (9H, s, SiMe3); δC (100 MHz, CDCl3)
169.2 (C), 156.9 (C), 147.9 (C), 142.3 (CH), 125.9 (CH),
110.8 (CH), 109.5 (CH), 60.5 (CH2), 23.6 (Me), 13.0 (Me),
0.0 (Me).
carboxylate 4k (Found MH+, 236.1651. C14H22NO2 requires
236.1650); νmax (film) 2974, 2932, 1721, 1594, 1562, 1162,
1092 cm-1; δH (400 MHz; CDCl3) 6.83 (1H, s, PyH), 2.54 (2H,
q, J 7.6, CH2), 2.45 (3H, s, Me), 2.44 (3H, s, Me), 1.53 (9H, s,
CMe3); δC (100 MHz, CDCl3) 171.2 (C), 160.7 (C), 156.5 (C),
152.6 (C), 130.4 (C), 123.1 (CH), 85.0 (C), 30.8 (Me), 28.8
(CH2), 27.1 (Me), 25.4 (Me), 17.4 (Me); tert-Butyl 2,6-
dimethyl-4-phenylpyridine-3-carboxylate 4l (Found MH+,
284.1647. C18H22NO3 requires 284.1650); νmax (film) 2976,
2928, 2855, 1722, 1588, 1551, 1138, 1089, 1031 cm-1; δH (400
MHz; CDCl3) 7.32 (5H, m, PhH), 6.91 (1H, s, PyH), 2.53 (3H,
s, Me), 2.50 (3H, s, Me), 1.22 (9H, s, CMe3); δC (100 MHz,
CDCl3) 168.9 (C), 159.1 (C), 155.7 (C), 148.9 (C), 139.7 (C),
129.2 (CH), 129.1 (CH), 129.0 (CH), 128.0 (CH), 122.0 (C),
82.4 (C), 28.1 (Me), 25.3 (Me), 23.6 (Me).
(9) Typical experimental procedure: A suspension of amberlyst
15 ion exchange resin (100 mg) in a solution of the enamine
(0.89 mmol) and alkynone (1.2 mmol) in toluene (3.5 mL) was
stirred at 50 °C overnight. The mixture was filtered, the solid
residue washed with chloroform (5 mL), and the filtrate
evaporated in vacuo and purified by flash chromatography on
silica to give the product.
(10) Ethyl 2,6-dimethyl-4-phenylpyridine-3-carboxylate4i (Found
MH+, 256.1334. C16H18NO2 requires 256.1337); νmax (film)
2926, 1724, 1588, 1552, 1083, 1024; δH (400 MHz; CDCl3)
Article Identifier:
1437-2096,E;2001,0,07,1149,1151,ftx,en;D09001ST.pdf
Synlett 2001, No. 7, 1149–1151 ISSN 0936-5214 © Thieme Stuttgart · New York