C—H bond oxidation reactions underscore the existing paradigm wherein high reactivity and high selectivity are inversely correlated. The development of catalysts capable of oxidizing strong aliphatic C(sp3)—H bonds while displaying chemoselectivity (i.e. tolerance of more oxidizable functionality) remains an unsolved problem. Herein, we describe a catalyst, manganese tert-butylphthalocyanine [Mn(tBuPc)], that is an outlier to the reactivity-selectivity paradigm. It is unique in its capacity to functionalize all types of C(sp3)—H bonds intramolecularly, while displaying excellent chemoselectivity in the presence of π-functionality. Mechanistic studies indicate that [Mn(tBuPc)] transfers bound nitrenes to C(sp3)—H bonds via a pathway that lies between concerted C—H insertion, observed with reactive noble metals (e.g. rhodium), and stepwise radical C—H abstraction/rebound, observed with chemoselective base metals (e.g. iron). Rather than achieving a blending of effects, [Mn(tBuPc)] aminates even 1° aliphatic and propargylic C—H bonds, reactivity and selectivity unusual for previously known catalysts.

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 inert, or 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.

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A novel manganese C‐H amination catalyst is easily synthesized in one step from commercially available materials.

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