Photocatalytic Synthesis of Indanone, Pyrone, and Pyridinone Derivatives with Diazo Compounds as Radical Precursors.

We disclose herein a photocatalytic radical cascade cyclization of diazoalkanes for the divergent synthesis of important carbocycles and heterocycles. Under the optimal reaction conditions, various indanone, pyrone, and pyridinone derivatives can be obtained in moderate to good yields. Mechanistic experiments support the formation of carbon-centered radicals from diazoalkanes through the proton-coupled electron transfer process. Scale-up reaction using continuous flow technology and useful downstream application of the formed heterocycles further render the strategy attractive and valuable.