A cobalt-catalyzed, regioselective cyclopropanation of polyolefins is reported. The reaction utilizes CH<sub>2</sub>Br<sub>2</sub> as a methylene source and Zn as a stoichiometric reductant. The large steric profile of the (PDI)Co catalyst (PDI = pyridine–diimine) allows substrates containing multiple alkenes to be selectively monocyclopropanated based on the substitution pattern of the alkene. The synthetic applications of this catalytic cyclopropanation are highlighted in a series of terpene natural product substrates. This method can also be applied to the synthesis of vinylcyclopropanes, which are useful strained rings used in a broad range of catalytic ring-opening reactions. Mechanistic studies suggest that the key carbenoid intermediate is a Co–Zn heterobimetallic complex.

Regioselective Simmons-Smith type cyclopropanations of polyalkenes under catalyst control

255th National Meeting (2018)

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