[2+2] Cycloadditions

[2+2] Cycloadditions furnish straightforward methods for the construction of four-membered rings, which are key motifs of numerous biologically significant natural and unnatural products. In recent decades, the employment of versatile chiral auxiliaries and catalysts prompted the development of asymmetric [2+2] cycloadditions. In this chapter, research advances of asymmetric [2+2] cycloadditions via auxiliary induced and catalytic strategies to access chiral four-membered carbo- and heterocyclic compounds are presented. Accordingly, the text is divided into several sections based on the structure of cycloadducts, including cyclobutanes, cyclobutenes, cyclobutanones, and four-membered heterocycles.