Copper-Catalyzed Coupling of Alkyl Vicinal Bis(boronic Esters) to an Array of Electrophiles

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.

Automated summary

This study discovered that a neighboring boronate group in the substrate can accelerate transmetalation to copper, enabling site-selective cross-couplings of organoboronic esters. The method is practical and allows for coupling between vicinal bis(boronic esters) and allyl, alkynyl, propargyl electrophiles, and simple protons. Mechanistic experiments suggest the involvement of chelated cyclic ate complexes in transmetalation.