Cyclobutane and Cyclobutene Synthesis: Catalytic Enantioselective 2+2 Cycloadditions

Cyclobutanes and cyclobutenes are important structural motifs found in numerous biologically significant molecules, and they are useful intermediates for chemical synthesis. Consequently, 2+2 cycloadditions to access cyclobutanes and cyclobutenes have been established to be particularly useful transformations. Within the last 10 years, an increase in the frequency of publications for catalytic enantioselective 2+2 cycloadditions has occurred. These reactions provide access to a wide array of enantiomerically enriched chemical diversity that was not previously attainable. Described in this review are the advances made in catalytic enantioselective 2+2 cycloadditions to access cyclobutanes and cyclobutenes.