Visible-light driven acetoxylation and dioxygenation of indoles via electron donor-acceptor complexes

A photoresponsive electron donor-acceptor (EDA) complex, formed by indole and hypervalent iodine such as diacetoxyiodobenzene (DAIB/PIDA, etc.), was detectable through absorption and emission spectroscopy. Irradiation of the EDA complex with visible light triggered photoinduced single electron transfer (SET) processes that were synthetically useful for the catalyst-free, regioselective acetylation of indoles. The photocatalytic reaction with excess DAIB was also used for the synthesis of isatins. The synthetic protocols were tolerant of a wide variety of substituents on the indole ring, including N-substitutions. DFT and TD-DFT studies were performed to model the excited states of the EDA complex and validate the photoinduced SET mechanism.

Automated summary

This paper reports a photoresponsive electron donor-acceptor (EDA) complex, which can be detected through absorption and emission spectroscopy. Irradiation of the EDA complex with visible light triggers photoinduced single electron transfer (SET) processes that are useful for the catalyst-free, regioselective acetylation of indoles. The photocatalytic reaction with excess DAIB is also used for the synthesis of isatins. DFT and TD-DFT studies are performed to model the excited states of the EDA complex and validate the photoinduced SET mechanism.