Iodine-Catalyzed Carbonyl Desaturation: A One-Pot Synthesis of Flavones.

Carbonyl desaturation represents a fundamental chemical transformation widely practiced in organic synthesis. Transition metal-catalyzed direct α,β-desaturation of carbonyl compounds has been well developed. Herein, we disclose an efficient one-pot synthesis of flavones from phenolic ketones via double iodine-catalyzed α,β-dehydrogenation and an oxa-Michael addition. This protocol is a metal-free approach to carbonyl desaturation with nontoxic DMSO as both the solvent and oxidant, which is especially beneficial for the synthesis of pharmaceutical compounds. Mechanistic studies suggest that the transformation proceeds via a radical pathway.