Methylenecyclopropanes are compounds containing a cyclopropane ring and an exocyclic double bond. Methylenecyclopropanes serve as versatile synthetic intermediates for various cycloaddition reactions and are present in biologically active compounds. Despite the importance of these molecules, there are few available methods to access methylenecyclopropanes in a single step. One potential strategy for the synthesis of a methylenecyclopropane entails the addition of a vinylidene to an olefin. However, the challenges associated with this strategy are, 1) the inherent unstability of the diazoalkenes as vinylidene precursors, and 2) the propensity of vinylidenes to undergo rapid isomerization to alkynes. We have developed an efficient catalytic synthesis of methylenecyclopropanes using a new class of dinuclear Ni complexes developed in our group. The reaction uses 1,1-dichloroalkene as a vinylidene precursor along with Zn as a stoichiometric reductant. A wide range of monosubstituted terminal alkenes and relatively unhindered internal alkenes are viable substrates. Furthermore, to understand the mechanism of vinylidene transfer, various stoichiometric and stereochemical experiments were performed. As an extension of this study, we found that the dinuclear Ni catalyst has the potential to catalyze vinylidene insertion reactions into Si–H and S–H bonds.

Catalytic reductive vinylidene transfer reactions

255th National Meeting (2018)

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