Photochemical Synthesis of Succinic Ester-Containing Phenanthridines from Diazo Compounds as 1,4-Dicarbonyl Precursors.

We disclosed herein a straightforward photochemical method for the construction of phenanthridines containing a synthetically useful succinate unit. The reaction occurred under visible-light irradiation with cheap eosin Y Na as photoredox catalyst and a diazo compound as the succinate precursor. Under the optimal reaction conditions, a wide range of phenanthridines were obtained in moderate to good yields. Note that the succinate units in the final heterocycles could be easily transformed into many valuable structures, such as γ-butyrolactone, dihydrofuran-2(3)-one, and tetrahydrofuran. Mechanistic experiments were performed to support the proposed mechanism.