Tandem aza-Wittig/carbodiimide-mediated annulation applicable to 1,2-diaza-1,3-dienes for the one-pot synthesis of fully substituted 1,2-diaminoimidazoles.

One-pot sequential aza-Michael, Staudinger, and aza-Wittig reactions on 1,2-diaza-1,2-dienes (DDs) can afford fully substituted 1,2-diaminoimidazoles. A plausible mechanism for the imidazole core formation involving an intramolecular ring closure of the carbodiimide-derived phosphazene intermediate is given. The reported strategy has sufficient flexibility to allow substituted 1,2-diaminoimidazoles with orthogonal nitrogen-protective groups to be generated from a variety of heterocumulene moieties linked to the DDs skeleton.