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completion of the addition, the reaction mixture was stirred for additional 5 min, and then
propargyl bromide (5.8 mL, 0.066 mol) was added via a syringe. Stirring was continued at 0 °C
for additional 3 h. The reaction mixture was then slowly poured into cold water and this mixture
was extracted with EtOAc three times. The organic layers were combined, washed with brine,
dried over MgSO4 and concentrated under vacuum. The resulting residue was purified by silica
gel flash chromatography (hexanes/EtOAc, 6 : 1, v/v) to afford the desired allenyne 74e (8.3 g,
77%) as a pale yellow solid (mp range 108.5-110.0 °C).
1 H NMR (300 MHz, CDCl3): δ 7.66-7.63 (m, 2H), 7.48-7.38 (m, 3H), 6.06 (t, J = 6.6 Hz, 1H),
4.96 (d, J = 6.6 Hz, 2H), 4.06 (d, J = 2.3 Hz, 2H), 3.75 (s, 3H), 2.43 (t, J = 2.4 Hz, 1H), 2.31 (dd,
J = 13.8, 5.8 Hz, 1H), 2.16 (dd, J = 13.8, 5.1 Hz, 1H), 1.91-1.76 (m, 1H), 0.99 (d, J = 6.7 Hz,
3H), 0.96 (d, J = 6.6 Hz, 3H); 13 C NMR (75 MHz, CDCl3): δ 207.7, 172.6, 171.6, 135.6, 130.5,
128.4, 127.3, 91.4, 81.1, 79.1, 73.0, 67.2, 52.3, 42.5, 37.8, 24.4, 24.1; IR (thin film): ν 3257,
2956, 2115, 1957, 1742, 1646 cm -1 ; MS m/z (%) 324 (76), 310 (55), 294 (45), 266 (35), 105
(100); EI-HRMS calcd for C20H22NO3 m/z [M] + 324.1600; found 324.1603.
BzN
MeO 2C
MeO
2-(Benzoylprop-2-ynylamino)-2-(4-methoxybenzyl)-penta-3,4-dienoic acid methyl ester
(74f). Prepared by following the procedure for preparation of 74e (vide ultra), using: 58e (17.5 g,
498 mmol), propargyl bromide (13.7 mL, 124 mmol), NaH (5.0 g of a 60% dispersion in mineral
oil, 124 mmol). Stirred at 0 °C for 2 h. Purification by flash chromatography (gradient elution,
hexanes/EtOAc, 9 : 1 to 1 : 1, v/v) afforded 74f (16.4 g, 84%).
1 H NMR (300 MHz, CDCl3): δ 7.67-7.64 (m, 2H), 7.46-7.42 (m, 3H), 7.17 (d, J = 8.6 Hz, 2H),
•
74f
179
H
H
H