Asymmetric Synthesis of Boryl-Functionalized Cyclobutanols

A diastereo- and enantioselective synthesis of boron-containing cyclobutanols is reported. We exploit an enantioselective borylcupration to generate a chiral benzylic copper intermediate that is intercepted with a proximally tethered ketone. The scaffolds contain an all-carbon quaternary center with a modular boronate moiety which allows access to a variety of synthetically valuable functional groups. This work represents an asymmetric approach to monocyclic cyclobutanols and highlights the utility of copper catalysis in the generation of small-sized rings.