SYNTHESIS OF β-VINYL-SUBSTITUTED 4Н-CHROMENES AND [4+2] CYCLOADDITION REACTIONS INVOLVING THEM

Abstract

β-Vinyl-substituted chromenes were obtained from 1H-benzo[f]chromene-2-carbaldehydes and 6-bromo-4H-chromene-3-carbaldehyde by the Wittig reaction. The Diels–Alder reaction of the β-vinyl-substituted chromenes with dimethyl acetylenedicarboxylate, ninhydrin, and diethyl 2,3-dicyanofumarate yielded spiro-substituted 3,10a-dihydro-2H,5H-pyrano[2,3-b]chromenes, derivatives of 7a,10-dihydro-12H-benzo[a]xanthene and 7a,8,10,12-tetrahydro-9H-benzo[a]xanthene.