Template-Directed Photochemical [2 + 2] Cycloaddition in Crystalline Materials: A Useful Tool to Access Cyclobutane Derivatives

The photochemical [2 + 2] cycloaddition reaction in crystalline materials is one of most important routes for the synthesis of cyclobutane compounds, which are otherwise difficult to prepare by conventional organic synthesis. In this perspective, a series of olefins that undergo photochemical [2 + 2] cycloaddition reactions is summarized and categorized according to their various functionality. Using these olefins, a range of cyclobutane derivatives were prepared by this [2 + 2] cycloaddition protocol.