Visible-Light Mediated Radical Alkylation of Flavones: A Modular Access to Nonsymmetrical 3,3″-Biflavones.

The first synthetic strategy for nonsymmetrical 3,3″-biflavones is described. To this end, a novel visible-light iridium-catalyzed radical C-3 alkylation of flavones with -methoxy phenacyl bromides was developed. Selective demethylation of the alkylated flavones and acylation through a Baker-Venkataraman rearrangement with diverse acyl chlorides afforded a library of 20 structurally novel biflavones. This modular strategy rapidly expands the structural complexity and diversity of these privileged scaffolds.