Cascade Amination: Synthesis of N -Nitrobenzenesulfonyl Benzimidazoles with DABSO as a Stable SO ₂ Surrogate

A cascade amination reaction of o-aminyl azobenzenes, benzaldehydes, diethyl sebacate, and DABSO is reported for synthesizing N-nitrobenzenesulfonyl benzimidazoles, catalyzed by TBAI under transition-metal-free conditions. DABSO functions as both a sulfonyl source and a rapid aminyl radical trap. The practical procedure features excellent compatibility with various susceptible functional groups and a broad substrate scope under mild and operationally simple conditions. Furthermore, the reaction can be readily scaled to gram quantities.