Flavan derivatives. XXXI. Reduction products from Isochromeno(4',3':2,3)-chromones

Abstract

Some reduction products (chromens, chroman-4-ols, and flavonols) obtained from isochromeno(4?,3?:2,3)chromone and its 7-methoxy derivative with lithium aluminium hydride, sodium di(2- methoxyethoxy)aluminium hydride, and catalytic hydrogenation are described. Allylic coupling is evident in isochromano(4?,3?:2,3)- chrom-3-ens, and the absence of allylic coupling in 3-alkoxyflav-3-enes is therefore attributed to the latter occurring in the conformation with the 2-aryl group axial (cf.¹).