The catalytic transformation of a C(sp3)–H bond to a C(sp3)–C bond via an iron carbene intermediate represents a long-standing challenge. Despite the success of enzymatic and small molecule iron catalysts mediating challenging C(sp3)–H oxidations and aminations via high-valent iron oxos and nitrenes, C(sp3)–H alkylations via isoelectronic iron carbene intermediates have thus far been unsuccessful. Iron carbenes have been shown to favor olefin cyclopropanation and heteroatom-hydrogen insertion. Herein we report an iron phthalocyanine-catalyzed alkylation of allylic and benzylic C(sp3)–H bonds. Mechanistic investigations support that an electrophilic iron carbene mediates homolytic C–H cleavage and rebounds from the resulting organoiron intermediate to form the C–C bond; both steps are tunable via catalyst modifications. These studies suggest that for iron carbenes, distinct from other late metal carbenes, C–H cleavage is partially rate-determining and must be promoted to effect reactivity.

Catalytic C(sp3)−H alkylation via an iron carbene intermediate

256th National Meeting (2018)

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