The [2 + 2] photocycloaddition between an electronically excited carbonyl compound and an alkene leading to oxetanes (Paternò-Büchi reaction) is one of the most investigated organic photochemical reaction. Regio-, stereo- and site selectivities are discussed as a consequence of the reaction mechanism. Spin multiplicity and electron transfer have a significant impact on the outcome of the reaction. Typical carbonyl and alkene reaction partners are presented indicating scope and limitation of the reaction. The Paternò-Büchi reaction possesses particular interest for being applied to organic synthesis, considering the difficulty for non-photochemical reactions to obtain oxetanes, with or without stereoselectivity. Mechanistic details are particularly focused. It has been applied as key step in various multi-step syntheses.

电子激发的羰基化合物与导致氧杂环丁烷的烯烃之间的[2 + 2]光环加成反应（Paternò-Büchi反应）是研究最多的有机光化学反应之一。由于反应机理，讨论了区域选择性，立体选择性和位点选择性。自旋多重性和电子转移对反应的结果有重大影响。给出了典型的羰基和烯烃反应伙伴，表明了反应的范围和局限性。考虑到非光化学反应难以获得具有或不具有立体选择性的氧杂环丁烷，Paternò-Büchi反应对有机合成特别感兴趣。机械细节特别受关注。它已被用作各种多步骤合成中的关键步骤。