Alkenes, Patemo-Biichi reaction aldehydes

The [2+2] photocycloaddition of an aldehyde or a ketone to an alkene to form an oxetane (e. g. Ill + IV —> V, Scheme 1) is a process that is known as the Patemo-Biichi reaction 8 it is a reaction that was first reported by Patemo in 19094 and was confirmed approximately forty-five years later by Biichi.Sa A particularly interesting variant of the Patemo-Biichi reaction is illustrated in... 

The [2 + 2] photocycloaddition of two alkenes is widely used to form cyclobutanes. The reaction proceeds in the forward direction because the product cannot absorb light of the wavelengths that the starting material can absorb. In the Patemo-Biichi reaction, one of the two-atom components is a ketone or an aldehyde instead of an alkene. Why these cycloadditions require light to proceed will be discussed later. 

Griesbeck and co-workers" described the first examples of oxazoles reacting as the alkene component in a Patemo-Biichi photocycloaddition reaction with aldehydes and a-ketoesters. The authors envisioned that such a process would generate... 

In 1909, Patemo and Chieffi noted that mixtures of tri- or tetra-substituted olefins and aldehydes formed trimethylene oxides when exposed to sunlight. Biichi later repeated Patemo s experiments by irradiating 2-methyI-2-butene in the presence of benzaldehyde, butyraldehyde, or aeetophenone and rigorously purifying and identifying the resulting products. The reaction thus bears the name of its two primary pioneers and has come to represent any photo-catalyzed [2 + 2] electrocyclization of a carbonyl and an alkene. 

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