Defluorinated Alkylation of α-Trifluoromethyl Alkenes and Benzyl Alcohol for the Synthesis of gem-Difluoroalkenes

Abstract

The catalytic activation of organic molecules using visible light photoredox catalysis has gained popularity recently. Photochemistry and photocatalysts have led chemists to investigate other radical precursors for producing reactive intermediates. One of the most widely accessible, functional groups in chemical synthesis in terms of commercial availability, synthetic diversity, and operational practicality is alcohol. However, the strategic use of alcohol as a radical precursor to create alkyl radicals remains unexplored. Furthermore, gem- difluoroalkenes, one of the extant fluorine-containing chemicals, are useful and cheaply available, and have been extensively studied in two-component coupling reactions. The synthesis of gem-difluoroalkenes via a photoredox catalysis strategy to produce α- trifluoromethyl alkenes using benzyl alcohol has not been reported. This study presents a novel method for constructing gem-difluoroalkene via visible-light photoredox catalyzed defluoronation reaction. Various trifluoromethyl alkenes and benzyl alcohol functional groups were tolerated and provide good to excellent yields. This strategy also conducted in mild condition, using metal-free photocatalyst and greener solvent. Mechanistic studies support a proposed reaction mechanism that involves single electron oxidation of benzyl alcohol.

Keywords Gem-difluoroalkenes • Alcohol • Visible-light • Photoredox catalysis