ABSTRACT
The first photocycloaddition of an aromatic carbonyl compound (benzaldehyde) to an alkene (2-methyl-2-butene) was published by Paterno` and Chieffi. They described this long-term experiment (104 days) with the words: ‘‘In una prima esperienza abbiamo esposto un miscuglio equimolecolare di amilene (gr. 43) e di aldeide benzoica (gr. 67) in un tubo chiuso, dal 5 dicembre 1907 al 20 marzo 1908, cioe` per circa tre mesi e mezzo della stagione invernale’’ [1]. This and other experiments were repeated by Bu¨chi and his coworkers in the mid-1950s and the oxetane constitution of the photogenerated product was confirmed [2]. The regioselectivity of this specific transformation, however was not correctly established until a publication by Yang et al. in 1964 [3]. In the following time, two features of this reaction were investigated in detail: the influence of the state properties of the electronically excited species and of the alkene properties on rate, efficiency, as well as selectivity of the oxetane formation. Furthermore, a detailed discussion of diastereo-and enantioselective modifications of intramolecular variants is presented in the following chapters. After discussion of the features of the carbonyl addends, the olefinic reaction partners are discussed. A number of extensive reviews about special features of this reaction type appeared in the last two decades which are recommended for further reading [4].
