Direct Deoxygenative Sulfonylation of Free Alcohols Enabled by Triphenylphosphine EDA Complexes

Abstract

Alkyl alcohols are widely used as bulk chemicals in industrial production and synthesis of high-value molecules, and there have been rapid advances in the transformation of alkyl alcohols to alkyl radical precursors. Methods for cleaving C–O bonds in alkyl alcohols require pre-functionalization of the hydroxyl group and rely on oxidants, reductants, or expensive photosensitizers, which limits the substrate scope. Thus, direct dehydroxylation of alcohols under mild conditions remains a major challenge. We report the first deoxygenative sulfonylation of free alcohols without oxidants, reductants, or photosensitizers. The electron donor–acceptor (EDA) complex formed between the thiosulfonate substrate and triphenylphosphine generates phosphine radical cations, which activate the hydroxyl group directly, achieving an efficient transformation. Alkyl alcohols of different degrees and with various substituents afford the target products in moderate to good yields demonstrating the broad compatibility of this method with alcohol substrates. We demonstrate the modification of pesticide molecules and synthesis of pharmaceutical molecules in one step using this strategy. Mechanistic studies confirm an EDA interaction between triphenylphosphine and thiosulfonate and that the reaction proceeds via a radical–radical coupling pathway.