Copper-Catalyzed C(sp3)−H α-Acetylation: Generation of Quaternary Centers

Abstract

α-substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in natural products and pharmaceuticals. We report the α-acetylation of C(sp³)−H substrates R−H with arylmethyl ketones ArC(O)Me to provide α-alkylated ketones ArC(O)CH₂R at RT with ^tBuOO^tBu as oxidant via copper(I) $$ -diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α-substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [Cu^II](CH₂C(O)Ar) that capture alkyl radicals R• to give R−CH₂C(O)Ar outcompeting dimerization of the copper(II) enolate to give the 1,4-diketone ArC(O)CH₂CH₂C(O)Ar.