ABSTRACT
A Pt-catalyzed enantioselective hydrosilylation of (Z)-1,2-diborylethylene provides a 1,2-diboryl-1-silylalkane that can be used in catalytic cross-coupling reactions. Depending on the catalyst employed and the cross-coupling reaction conditions, the coupling can occur at either α or ß relative to the silane center.
ABSTRACT
A neighboring boronate group in the substrate provides a dramatic rate acceleration in transmetalation to copper and thereby enables organoboronic esters to participate in unprecedented site-selective cross-couplings. This cross-coupling operates under practical experimental conditions and allows for coupling between vicinal bis(boronic esters) and allyl, alkynyl, and propargyl electrophiles as well as a simple proton. Because the reactive substrates are vicinal bis(boronic esters), the cross-coupling described herein provides an expedient new method for the construction of boron-containing reaction products from alkenes. Mechanistic experiments suggest that chelated cyclic ate complexes may play a role in the transmetalation.
Subject(s)
Copper , Esters , Alkenes/chemistry , Boron/chemistry , Boronic Acids/chemistry , Catalysis , Copper/chemistry , Esters/chemistry , Molecular Structure , ProtonsABSTRACT
Chiral 1,2-bimetallic reagents are useful motifs in synthetic chemistry. Although syn-1,2-bimetallic compounds can be prepared by alkene dimetallation, anti-1,2-bimetallics are still rare. The stereospecific 1,2-metallate shift that occurs during conjunctive cross-coupling is shown to enable a practical and modular approach to the catalytic synthesis of enantioenriched anti-1,2-borosilanes. In addition to reaction development, the synthetic utility of anti-1,2-borosilanes was investigated, including applications to the synthesis of anti-1,2-diols and anti-1,2-amino alcohols.
