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Stereospecific Transformations of Alkylboronic Esters Enabled by Direct Boron-to-Zinc Transmetalation
1Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States.
Abstract:
Chiral secondary organoboronic esters, when activated with t-butyllithium, are shown to undergo efficient stereoretentive transmetalation with either zinc acetate or zinc chloride. This reaction provides chiral secondary alkylzinc reagents that are configurationally stable under practical experimental conditions. The organozinc compounds were found to engage in stereospecific reactions with difluorocarbene, catalytic cross-couplings with palladium-based catalysts, and trifluoromethylation with a copper(III) complex. Mechanistic and computational studies shed light on the inner workings of the transmetalation event.
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