Photochemical process leading to the formation of cyclobutanols by cycloaddition of an alkene to a 1,3-dicarbonyl-enol. The enol originates in most cases from the tautomerization of a 1,3-dicarbonyl compound. The products of the de Mayo reaction are susceptible to undergo a retro-aldol ring opening resulting in the formation of 1,5-dicarbonyl compounds.
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 322 (https://doi.org/10.1351/pac200779030293)