Olefination of Alkyl Halides with Aldehydes by Merging Visible-Light Photoredox Catalysis and Organophosphorus Chemistry.

Carbon-carbon double bond (C=C) formation is a crucial transformation in organic chemistry. Visible-light photoredox catalysis provides economical and sustainable opportunities for the development of novel and peculiar organic reactions. Here we report a method for the olefination of alkyl halides with aldehydes by visible-light photoredox catalysis using triphenylphosphine as a reductive quencher (103 examples). This transformation accommodates a variety of aldehydes including paraformaldehyde; aqueous formaldehyde; 2,2,2-trifluoroacetaldehyde monohydrate; 2,2,2-trifluoro-1-methoxyethanol; and other common aldehydes. The present method exhibits several advantages, including operational simplicity, mild reaction conditions, wide functional group tolerance, and amenability to gram-scale synthesis. We anticipate that it will be widely used in the synthesis of organic molecules, natural products, biological molecules, and polymers.