Bromide-Promoted Visible-Light-Induced Reductive Minisci Reaction with Aldehydes

Abstract

Radical addition is a robust tool for bond formation. While ketyl radical reactivity of aldehydes by photoredox has been well-established, herein, we have now revealed a pathway for umpolung addition of aldehydes with or without external reductant. Hence, the reductive alkylations and challenging benzylations of nitrogen heteroarenes (i.e., Minisci reactions) are enabled by the bromide-promoted visible light-mediated photocatalysis. The present protocol offers a mild, viable method for late-stage alkylations and transition-metal-free benzylations of biologically active nitrogen-heteroarene molecules. Mechanistic studies are indicative of a bromide-initiated acyl radical mechanism in the absence of external reductant.