Sustainable photoredox chemistry of a transient ternary complex: an unconventional approach toward trifluoromethylated hydroquinones

Abstract

A distinctive sustainable approach has been developed to afford highly functionalized CF₃–hydroquinone derivatives as potent biologically active molecules. The synthetic protocol involves the photoirradiation of a mixture of easily accessible benzoquinones and CF₃SO₂Na. This process generates a quinhydrone charge-transfer complex of benzoquinone and its in situ generated hydroquinone in the presence of a small amount of hydrogen donors, more preferably water. The subsequent formation of a transient ternary complex involving CF₃SO₂Na elicits photoinduced charge-transfer (CT), thereby producing CF₃–hydroquinones. The present method is highly practical and atom-economical whilst avoiding the use of any sacrificial electron donors. Furthermore, the unique ternary complex intermediate permits site-selective three-component trifluoromethylation in the presence of vinyl arenes.