Diastereoselective Synthesis of Monofluorocyclohexenes through Photocatalyzed Cascade Cyclization of gem-Difluoroalkenes and α,β-Unsaturated Carbonyl Compounds.

Monofluoroalkenes are nonhydrolyzable mimetics of amides. Previous work focused on the synthesis of non-cyclic monofluoroalkenes. However, diastereoselective synthesis of monofluorocyclohexenes from non-cyclic substrates is challenging. Herein, we report the first photocatalyzed cascade cyclization reactions of readily available α,β-unsaturated carbonyl compounds and gem-difluoroalkenes for the synthesis of highly functionalized monofluorocyclohexenes. The reaction shows broad substrate scope with high diastereoselectivity (>30 examples, up to 86 % yield, >20 : 1 dr). The post-reaction transformations of the products demonstrate the synthetic potential of this methodology.