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dispersion in mineral oil, 1.0 mmol), propargyl bromide (80% wt. in toluene, 92 µL, 0.83 mmol).
Purification by flash chromatography (hexanes-EtOAc, 6 : 1, v/v) afforded 73b (143 mg, 73%)
as a mixture of diastereomers in a ~1.7 : 1 ratio determined by integration of the methyl group
resonances in the 1 H NMR spectrum.
1 H NMR (300 MHz, CDCl3): δ 7.67-7.62 (m, 2H), 7.49-7.39 (m, 3H), 7.28-7.23 (m, 5H), 5.85
(sex, J = 3.1 Hz, 1H), 5.56-5.41 (m, 1H), 3.97 (d, J = 13.5 Hz, 0.63H), 3.96 (d, J = 13.6 Hz,
0.37H), 3.76 (s, 1.1H), 3.76 (s, 1.9H), 3.72 (dt, J = 18.9, 3.0 Hz, 1H), 3.51 (dt, J = 18.8, 3.0 Hz,
1H), 3.42 (d, J =13.6 Hz, 0.63H), 3.41 (d, J = 13.6 Hz, 0.37H), 2.14 (t, J = 2.4 Hz, 0.63H), 2.12
(t, J = 2.4 Hz, 0.37H), 1.81 (dd, J = 7.2, 3.2 Hz, 1.9H),1.75 (dd, J = 7.1, 3.2 Hz, 1.1H); 13 C NMR
(75 MHz, CDCl3): δ 205.0, 172.7, 171.7, 136.7, 136.6, 136.2, 131.4, 130.7, 128.7, 128.4, 127.5,
127.1, 91.1, 91.0, 90.7, 81.2, 72.9, 72.9, 69.2, 52.7, 52.7, 39.3, 39.2, 14.1, 13.8; IR (thin film): ν
2948, 2118, 1968, 1743, 1643 cm -1 ; MS m/z (%) 372 (50), 282 (40), 105 (100); EI-HRMS calcd
for C24H22NO3 m/z [M] + 372.1600; found 372.1613.
BzN
MeO 2C
Bn
73c
2-[Benzoyl(3-trimethylsilylprop-2-ynyl)amino]-2-benzylhexa-3,4-dienoic acid methyl ester
(73c). To a solution of 58a (243 mg, 0.723 mmol), in THF (7 mL) was added KH (90 mg of 35%
wt. dispersion in mineral oil, 0.80 mmol) at rt, followed by addition of (3-bromoprop-1-ynyl)-
trimethylsilane (203 µL, 1.44 mmol). The reaction mixture was stirred at rt for 12 h and then
carefully poured into a beaker containing EtOAc and water. The aqueous layer was extracted
with EtOAc and organic layers were combined, washed with brine (20 mL), dried over MgSO4,
and concentrated under vacuum. Purification by flash chromatography (hexanes-EtOAc, 9 : 1,
•
TMS
v/v) afforded 73c (240 mg, 75%) as a mixture of diastereomers.
169
H