Dication C(R1)–N(R2)2 Synthons and their use in the Synthesis of Formamidines, Amidines, and α-Aminonitriles

A combination of amides and 2-pyridinesulfonyl chloride was evaluated as synthons of the dication C(R1)–N(R2)22+. When the substrates were primary amines, high yields of formamidines and amidines were obtained. When the substrates were α-aminoamides, α-aminonitriles were obtained. Through this process, naturally occurring α-aminoacids can be transformed into chiral α-aminonitriles with complete retention of stereochemical configuration. All reactions proceed rapidly at room temperature, and normally finish within 10 min, with yields ranging from 80 to 95% for most cases. Among the sulfonyl chlorides examined, 2-pyridinesulfonyl chloride stands out in both reaction rate and selectivity of formamidine or amidine versus sulfonyl amide. The scope and limitations of the reaction among different types of amides as synthons and amines as substrates were examined.