Paterno-Buchi Reaction

In 1909, the Italian chemist Emanuele Paternò di Sessa reported an interesting reaction between benzaldehyde and
2-methyl-2-butene on exposure to sunlight. Two isomeric compounds were isolated from the reaction that were characterized as trimethylene oxides or oxetanes. In 1954, the Swiss chemist George Hermann Büchi decided to
re-examine this earlier work and identify the exact structure of the products. Subsequently, the photochemical cycloaddition between aldehydes and alkenes to form oxetanes became known as the Paterno-Büchi reaction. During the reaction, the carbonyl substrate, which can be either an aldehyde or ketone, absorbs energy and adds across the carbon-carbon double bond of the alkene.

The reaction is useful synthetically as it is highly regio- and stereoselective, and has subsequently been used in several total synthesis campaigns. For example, during the first total synthesis of the cytotoxic agent (±)-euplotin A, the correct stereochemistry of the required dihydrofuran substrate was established via the Paterno-Büchi reaction between ethyl glyoxylate and furan.