STEREOSELECTIVE SYNTHESIS OF FUNCTIONALIZED BUTENOLIDES BY THE PHOTOCHEMICAL-REARRANGEMENT OF [2,1]BENZISOXAZOLEQUINONE DERIVATIVES

On direct irradiation 3-alkoxy[2,1]benzisoxazolequinones 1a, 1b, 1c, 1 e and 3-N,N-dimethylamino[2,1]benzisoxazolequinone 1d undergo rearrang ement to the corresponding gamma-cyano alkylidenebutenolides 3 in high yield. The reaction is highly stereoselective for compounds la, Ib, I c, and Id yielding the corresponding Z-butenolides 3 as the only stere oisomer. A mechanism involving triplet nitrene intermediates is propos ed for the reaction. (C) 1997 Elsevier Science Ltd.