Decarboxylative Giese-Type Reaction of Carboxylic Acids Promoted by Visible Light: A Sustainable and Photoredox-Neutral Protocol

Abstract

We describe herein a transition-metal-free method for the decarboxylative generation of radicals from carboxylic acids and their 1,4-addition to Michael acceptors. The Fukuzumi catalyst (9-mesitylene-10-methylacridinium perchlorate, [Acr-Mes]ClO4) enabled this transformation under visible-light irradiation at room temperature with CO2 as the only byproduct. The scope and limitations of this protocol were examined by using a range of Michael acceptors (15 examples) and carboxylic acids (18 examples). The use of 3-hydroxypivalic acid in this protocol allowed the straightforward formation of a diastereomerically pure δ-lactone. Moreover, when a homoallylic acid was used, a radical cascade reaction took place with the formation of three C–C bonds.