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.