Photochemical construction of chromanone‐fused estrones using a biphasic tandem rearrangement–cyclization approach

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‐ nor estrone 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.