Light-mediated catalytic enantioselective difluoroalkylation of β-ketoesters via phase-transfer catalysis

Abstract

We report a phase-transfer-catalysed asymmetric α-difluoroalkylation of β-ketoesters through visible light-promoted radical generation. This methodology affords quaternary stereocentres with mild enantioenrichment and isolated yields up to 99%. Through mechanistic investigations, we have determined that the reaction proceeds via difluoroalkyl radical generation arising from an in situ electron donor–acceptor complex capable of absorbing visible light. Extensive optimisation of the reaction parameters was carried in an attempt to overcome a facile racemic background reaction.