Bis-amidines as useful building blocks for heterofulvenes and -fulvalenes

An easily feasible synthesis for bis-amidines of type 3 was developed via a n aminolysis reaction of imidoyl chlorides 1 with gaseous ammonia. Dependin g on the nature of the electrophilic cyclization reagent, these amidines sh ow a different reactivity. On treatment with orthoesters, the fused imidazo les 5 were obtained which involved the participation of two different kinds of nitrogen atoms in the cyclization. In contrast to this, carboxylic acid chlorides are able to react selectively at the NH2-groups under formation of the fulvenoid 4H-imidazoles 6. The same regioselectivity was observed fo r chlorodimethylimmonium chloride thus leading, via the dimerization of cyc lic orthoamides, to the 1,4,5,8-tetraazafulvalenes 8.