Chiral Induction in [2+2+2] Cycloaddition Reactions

Chiral compounds containing six-membered rings, whether aromatic or not, are of interest in a wide range of disciplines, including material science, medicinal chemistry, and agrochemistry. As transition-metal-catalyzed [2+2+2] cycloaddition reactions are one of the most elegant routes for the construction of six-membered rings, significant effort has been given to developing asymmetric variants. In this focus review, we bring together the work that has been done in optimizing diastereoselective [2+2+2] cycloaddition reactions of enantiomerically pure substrates. Two different approaches—chirality induction and chirality transfer—are considered in a review organized by the type of chiral element being constructed (central, axial, or helical). The general challenges that are involved are highlighted and possible future directions in the field are discussed.