Csp²–Csp² and Csp²–N Bond Formation in a One-Pot Reaction between N-Tosylhydrazones and Bromonitrobenzenes: An Unexpected Cyclization to Substituted Indole Derivatives

A novel, sequential, palladium-catalyzed, cross-coupling reaction using N-tosylhydrazone and bromonitrobenzene derivatives followed by reductive cyclization has been developed. This transformation providing an efficient route to unexpected N-arylindole derivatives involves, in a one-pot reaction, the formation of one Csp²–Csp² bond and two Csp²–N bonds together with the cleavage of one Csp²–heteroatom bond. Evaluation of the biological activity led to the identification of compound 5a, which displays potent activity at nanomolar concentrations against human colon carcinoma cell line.