Enantioselective Palladium-Catalyzed [3+2] Cycloaddition of Trimethylenemethane and Fluorinated Ketones.

A nitrile-substituted trimethylenemethane (TMM) donor undergoes palladium-catalyzed [3+2] cycloadditions with fluorinated ketones to generate tetrasubstituted trifluoromethylated centers in high enantioselectivity under mild conditions. The generation of the palladium-TMM complex was achieved by a self-deprotonation strategy, which shows remarkable improvements in regiocontrol, efficiency, and atom economy of asymmetric [3+2] cycloadditions. Moreover, the versatility of the nitrile group provides direct access to a variety of synthetically useful intermediates, including amides, aldehydes, and esters. The developed reaction conditions allow for the synthesis of a wide variety of aromatic, heteroaromatic, and aliphatic fluorinated dihydrofurans in excellent regio- and enantioselectivities.