反应详情

To a mixture of 71, (2.7 g, 15 mmol) and trimethyl orthoformate (5 mL) was added p-TSA, (anhydrous, 255 mg, 1.5 mmol). The mixture was refluxed for 3 h and the excess trimethyl orthoformate evaporated under reduced pressure. The crude product was purified over a column of silica gel, eluting with 30% acetone-petroleum ether to give 72 as a colorless liquid (1.4 g), in 49% yield (two steps). 1H NMR (500 MHz, CDCl3) δ 8.43 (s, 1H), 7.39-7.31 (m, 5H), 4.77 (s, 2H), 4.64 (s, 2H).

1. temperatureThe mixture was refluxed for 3 h
2. customthe excess trimethyl orthoformate evaporated under reduced pressure
3. customThe crude product was purified over a column of silica gel
4. washeluting with 30% acetone-petroleum ether