Construction of Chiral Quaternary Carbon Centers via Asymmetric Metal Carbene gem-Dialkylation.

The catalytic asymmetric construction of all-carbon quaternary stereocenters has received tremendous interest over the past decades, and numerous efficient protocols have been disclosed based on the formation of one C-C bond between two assembling reactants. However, the use of asymmetric multi-component reactions that build two C-C bonds on the same carbonic center with concomitant assembly of quaternary stereocenters is rare and remains challenging. Herein, we disclose an enantioselective three-component reaction of α-diazo ketones with alkenes and 1,3,5-triazines under dirhodium/chiral phosphoric acid cooperative catalysis, which leads to a practical and atom-economic synthesis of poly-functionalized chiral ketones that bear a α-quaternary stereocenter in generally good to high yields with excellent enantioselectivities. In comparison to the previous method for the construction of tertiary and quaternary stereocenters via carbene gem-difunctionalization reactions, this reaction features an unprecedented gem-dialkylation process via sequential installation of two C-C bonds on the carbene center in one reaction, providing an essential complement to the asymmetric construction of all-carbon quaternary stereocenters using common and readily available starting materials.