Photochemistry of Carbonyl Compounds: Application in Metal-Free Reactions

Synthetic organic photochemistry is an efficient and environmentally friendly alternative to assemble biologically and chemically relevant scaffolds. The photon energy allows access to reactive intermediates by using a clean energy source under mild conditions. Moreover, sustainable synthesis can be achieved by using metal-free photochemistry. In this review, the photochemistry of carbonyl compounds and their application as reagents, catalysts or promoters of metal-free photochemical transformations are discussed. Fundamental aspects and reactivity of the carbonyl compounds are briefly presented in the introduction section, followed by recent applications of carbonyl compounds in photochemical reactions. The text is organized according to the role of the carbonyl compounds in the process. First, approaches in which carbonyl compounds are employed in stoichiometric or super-stoichiometric amounts (as reaction substrates or photoinitiators) are described. Thereafter, their application as photocatalysts and photosensitizers are discussed and mechanistic studies are comprehensively presented.