Catalyst-free aroylation of maleimides through C_sp²-H functionalization with aldehydes and benzyl phenyl sulfides

Aroyl maleimides and their derivatives have potential applications as inhibitors, fluorophores, antibiotics, and anticonvulsants. The Friedel-Crafts method, as the renowned aroylation method of arenes and heteroarenes, is tedious and suffers from harsh conditions, incompatibility with electron-deficient substrates, and Lewis acid deactivation due to its coordination with the nitrogen of substrates. Hence, two eco-friendly and feasible metal-free di-tert-butyl peroxide-promoted methods are developed for the aroylation of maleimides toward 3,4-diaroyl maleimides and 3-amino-4-aroyl maleimides. These include the direct cross-dehydrogenative coupling of maleimides with aryl aldehydes and the tandem oxidative C-S cleavage/cross-dehydrogenative coupling of benzyl phenyl sulfides with maleimides. The results indicate the efficiency of the presented approaches with broad scopes.