A common route to primary amidines is the Pinner reaction. Reaction of the nitrile with alcohol in the presence of acid gives an iminoether. Treatment of the resulting compound with ammonia then completes the conversion to the amidine. Instead of using a Bronsted acid, Lewis acids such as aluminium trichloride promote the direct amination of nitriles. They are also generated by amination of an imidoyl chloride.
They are also prepared by the addition of organolithium reagents to diimines, followed by protonation or alkylation.
Dimethylformamide acetal reacts with primary amines to give amidines:
:MeNC(H)(OMe) + RNH → MeNC=NHR + 2 MeOH