Visible-light-promoted cascade cyclization towards benzo[d]imidazo[5,1-b]thiazoles under metal- and photocatalyst-free conditions

Abstract

The visible-light-promoted cascade cyclization of 2-haloaryl isothiocyanates and isocyanides to access benzo[d]imidazo[5,1-b]thiazoles has been realized efficiently under metal- and photocatalyst-free conditions. The reaction mechanism was explored by several preliminary experiments involving reactive intermediate, free radical inhibitors, and corresponding photoelectric spectra. This protocol possesses some advantages over the previous methods such as readily available and inexpensive substrates, metal catalyst-free, step and atom economy, and mild reaction conditions.