Light-Assisted Oxidative Functionalization of Indoles by Re-(I)Dipyrrinato Catalyst

This work is focused on the photocatalytic chemodivergent oxidation of indoles by Re(I)dipyrrinato complex. Due to strong absorption in the visible region and high singlet oxygen quantum yields, the Re(I)dipyrrinato complexes can act as highly efficient photocatalysts. A chemodivergent photooxidation of indoles was demonstrated under an oxygen atmosphere featuring low catalyst loading (0.25 mol%) and short reaction time with blue LEDs. A variety of substrates viz., 3-methyl indoles, 2,3-dimethylindoles, N-protected indoles, and 2-methylindoles were utilized to produce N-(2-acetylphenyl)formamide, N-(2-acetylphenyl)acetamide, N-(2-formylphenyl)acetamide, and 2,2-disubstituted indoline-3-ones, respectively, in good to high yields. Mechanistic investigations revealed that the Re(I)dipyrrinato complex in the excited state is involved via photoinduced electron transfer (PET) and energy transfer (EnT) in these reactions. The method is notable for its mild conditions, operational simplicity, and wide scope, suggesting the potential application of Re(I)dipyrrinato complex as an advantageous photocatalyst.