Harnessing the Power of the De Mayo Reaction: Unveiling a Photochemical and Photocatalytic Masked [2+2] Methodology for Organic Synthesis

Abstract In 1962, Paul J. de Mayo initially described the photochemical reaction involving 1,3‐diketones and double bonds, resulting in the formation of 1,5‐diketones. Since then, this reaction has been extensively utilized for the synthesis of a wide range of fascinating natural products. Over time, this synthetic methodology has been applied to various carbonyl systems, including locked enol‐tautomers of diketones, β‐keto esters, and β‐enaminones. Additionally, it has found application in other unsaturated systems such as allenes and alkynes. In this review article, we provide a comprehensive overview of the classical de Mayo reaction, highlighting its scope and potential. Furthermore, we focus on recent advances achieved through photocatalytic conditions. Special emphasis is placed on the regioselectivity of the process and the underlying reaction mechanism, particularly within the context of photocatalysis.