Photoredox-Mediated Decarboxylative Radical Additions to 1,7-enynes. A Cascade Approach to Heterocyclic Compounds

Cascade reactions are highly valuable strategies for the preparation of (hetero)cyclic compounds since complex structures can be generated in a single operation, through controlled multiple bond forming steps. These approaches feature a more economic overall process and minimize the waste generation, following the principles of sustainable chemistry. In this regard, 1,7-Enynes are recognized as highly versatile substrates for construction of (hetero)cyclic scaffolds, therefore many strategies of radical cascade cyclizations have been recently reported.1 Decarbonylative and decarboxylative strategies allows the generation of alkyl radicals that trigged the cascade sequence. Most of the previous reports employed peroxides as oxidants and high temperatures to promote the initiation step, a combination that can limit their application.1 Here we present our studies on photocatalytic approaches employing N-(Acyloxy)-Phthalimides as alkyl radical sources.2 Notably, by tuning the reaction conditions, we were able to access two complementary scaffolds in promising yields starting from the same starting materials.