A four-component coupling of alkenylboronic esters, organolithium reagents, ketenes, and heteroatomic electrophiles yielding highly substituted tertiary β-boryl ketones is described. The reaction proceeds via ketene-triggered metallate rearrangement of alkenylboronic ester ate-complexes and subsequent electrophilic trapping of the resulting boron enolate, forming two carbon-carbon bonds and one carbon-heteroatom bond. This method provides expeditious access to diverse β-boryl carbonyl derivatives from simple building blocks.
Mizoguchi et al. (Fri,) studied this question.