Activation and Functionalization of C–C σ Bonds of Alkylidene Cyclopropanes at Main Group Centers

Aluminum­(I) and magnesium­(I) compounds
are reported for the C–C
σ-bond activation of strained alkylidene cyclopropanes. These
reactions result in the formal addition of the C–C σ
bond to the main group center either at a single site (Al) or across
a metal–metal bond (Mg–Mg). Mechanistic studies suggest
that rather than occurring by a concerted oxidative addition, these
reactions involve stepwise processes in which substrate binding to
the main group metal acts as a precursor to α- or β-alkyl
migration steps that break the C–C σ bond. This mechanistic
understanding is used to develop the magnesium-catalyzed hydrosilylation
of the C–C σ bonds of alkylidene cyclopropanes.