反应详情

The crude 6,6-dichloro-7-oxobicyclo[3.2.0]hept-2-en-2-carboxylic acid (61 g) from Example 3 was stirred as a suspension in 300 mL of ethyl acetate and treated portionwise with 57 g of diphenyldiazomethane over a 45 min period. The resulting solution was stirred at room temperature for 1 hr. Evaporation of the solvent and trituration with ether afforded 76.9 g (71.9%) of 6,6-dichloro-7-oxobicyclo[3.2.0]hept-2-en-2-carboxylic acid diphenylmethyl ester. Material prepared by essentially the same procedure had the following characteristics: IR (Nujol mull): 1625, 1730, 1800 cm-1 ; NMR (CDCl3): δ 3.07 (1H, dddd, J=20, 8, 2, 2), 3.20 (1H, broad d, J=20), 3.64 (1H, ddd, J=8, 8, 2), 4.89 (1H, ddd, J=8, 4, 2), 6.86 (1H, s), 6.95 (1H, dd, J=4, 2), and 7.2-7.5 (10H, m). HRMS: Calcd for C21H16O3Cl2, 386.0475; found, 386.0495.

1. customEvaporation of the solvent and trituration with ether