Photochemistry of 2-Oxoacetates: from Mechanistic Insights to Profragrances and Bursting Capsules

Abstract

Photoirradiation of 2-oxoacetates (α-ketoesters) with UV-A light proceeds via an intramolecular hydrogen abstraction of the triplet state in a Norrish type II pathway to form carbonyl compounds, carbon monoxide and/or dioxide, and a series of other side products. This review gives a detailed overview of the mechanistic aspects of photooxidation by explaining the pathways that yield the major products formed in the presence or absence of oxygen. Furthermore, it demonstrates how the photoreaction can be used for the light-induced controlled release of fragrances from non-polymeric profragrances, polymer conjugates and core-shell microcapsules in applications of functional perfumery. In the case of microcapsules, the gas formation accompanying the Norrish type II fragmentation can generate an overpressure that expands or cleaves the capsule wall to release fragrances and thus provides access to multi-stimuli responsive delivery systems.