Photochemical construction of chromanone-fused estrones using a biphasic tandem rearrangement-cyclization approach.

Abstract

A facile photochemical preparation of 4-chromanone fused to estrone has successfully been achieved upon direct irradiation with light of 254 nm under a nitrogen atmosphere employing 3-(2'-alkenoyl)estrone and 3-(2'-alkenoyl)-17-norestrone derivatives as optimal substrates. The two-phase acid- and base-catalyzed method relies upon two consecutive pathways in a one-pot fashion, involving the photo-Fries rearrangement reaction and a catalyzed intramolecular oxa-Michael addition to afford the desired 4-chromanone fused products in good yields.