反应详情

Reaction Scheme 2 proved to be useful for preparing compounds with different substituents at the 8-position of the dihydrofuro[3,2-f]-1,2-benzisoxazole nucleus. In this process, a dihydrobenzofuran intermediate (5) (prepared in Scheme 3) was subjected to a Friedel-Crafts reaction with o-fluorobenzoyl chloride to give the benzophenone intermediates (6) or (7). Use of mild reaction conditions in this acylation reaction gave the methyl ether (6) whereas more vigorous conditions led directly to the demethylated product (7). Reaction of the benzophenone (7) with hydroxylamine hydrochloride gave the corresponding oxime (8) which was converted to the oxime acetate (9) with acetic anhydride. Cyclization to (10) was achieved by treatment of the oxime acetate intermediate (9) with sodium hydride in N,N-dimethylformamide solution. The final carboxylic acid derivatives (11) were obtained from (10) by a hydrolysis reaction using potassium hydroxide in aqueous ethanol.

1. customReaction Scheme 2