First Practical Synthesis of Formamidine Ureas and Derivatives

Isonitriles and ureas undergo a condensation reaction in the presence of acid chlorides to give formamidine ureas, for which no general
synthetic routes currently exist. A mechanism is proposed in which the key intermediate is an electrophilic adduct of isonitrile and acid
chloride. The process is tolerant of moderate variability in the nature of the components, and access to formamidine ureas of varying substitution
patterns is further enhanced by a facile exchange reaction with amines.