Preparation and reactions of N-alkyl(aryl), N-isothiocyanatomethyl carboxamides: synthesis of 1,3,5-thiadiazepin-6-ones

N-Alkyl(aryl),N-isothiocyanato carboxamides 3 are prepared by the reaction of the corresponding 2-chloroacetamides 1 with potassium thiocyanate. In the case of N-aryl substitution the intermediate thiocyanates 2 could be isolated. These thiocyanates isomerize to isothiocyanates 3 at different rates depending on aryl substituents, temperature and solvents. The reaction between 3k and a nucleophilic agent (e.g. methanol, isopropylthiol, sodium hydrogensulfide, or ethyl malonate) results in the corresponding 1,3,5-thiadiazepin-6-ones, 5 by ring closure.