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.