Novel Synthesis of Heterocyclic Aryl Amidines.

We have developed a novel amidine synthesis that allows the preparation of heterocyclic amidines that were previously unknown and difficult to prepare by published methods. The route involves the lithiation of heterocycles by the action of n-BuLi followed by reaction with carbon disulfide and trapping with methyl iodide, yielding a dithioate ester. The latter, when heated in 20% methanolic ammonia at 80°C in a sealed tube provides the heterocyclic amidines directly, in good yield. The products are isolated by crystallization of the respective hydrochloride salts.