Intermolecular Chirality Transfer from Silicon to Carbon:  Interrogation of the Two-Silicon Cycle for Pd-Catalyzed Hydrosilylation by Stereoisotopochemical Crossover

A “two-silicon cycle” for the highly efficient intermolecular chirality transfer from silicon to carbon (98−99% ct) in the palladium-catalyzed hydrosilylation of norbornenes emerges from an investigation involving catalytic crossover experiments with isotopically labeled silicon-stereogenic silanes. A key outcome of these experiments, which are supported by product-distribution modeling, is the conclusion that the chirality transfer arises from thermodynamically controlled reversible silapalladation of the alkene rather than from kinetic control during irreversible σ-bond metathesis of the resulting β-silyl σ-alkyl palladium complex with chiral silane.