We describe the direct construction of all-carbon quaternary stereocenters via α-photoalkylation of β-ketocarbonyls with high efficacy and enantioselectivities by merging photoredox catalysis and primary amine catalysis. The open-shell photoradical approach enables asymmetric α-alkylations that are difficult under thermal conditions.
The communication describes an enamine-based asymmetric retro-Claisen reaction of β-diketones by primary amine catalysis. The reaction proceeds via a sequence of stereoselective C-C formation, C-C cleavage, and a highly stereospecific enamine protonation to afford chiral α-alkylated ketones or macrolides with high yields and enantioselectivities. A detailed mechanism was explored on the basis of experimental evidence and computational studies to account for the observed stereocontrol.
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