C-H Sulfenylation of Umpoled Indoles under Photocatalytic Conditions

Abstract

Organosulfur compounds, particularly those having sulfenyl group at C3 position of indoles have a number of interesting biological activity. By employing N-acyloxyindoles as the umpoled coupling partner, we developed herein two photocatalytic methods for direct C3-sulfenylation with unmodified thiol derivatives as the sulfenylating agents. Photolysis of N-acyloxyindoles with purple LEDs (405 nm) produced C3-sulfenylated products both with aryl and alkyl thiols. The reaction was proposed to occur by homolysis, followed by a radical chain pathway. Alternatively, irradiation of blue LEDs in the presence of Ru(bpz)32+ as the photocatalyst led to C3-sulfenylation products both with aryl and alkyl thiols. In this case, photocatalytic single electron transfer may generate a thiyl radical which initiates the chain pathway.