A fast and parallel route to cyclic isothioureas and guanidines with use of microwave-assisted chemistry.

A fast and simple approach to novel cyclic isothioureas and related guanidine derivatives is presented in this study. The construction of the central basic scaffolds is achieved solely by the application of microwave-assisted chemistry, without any need of activating agents or protecting group manipulations. The product formation of various substituted guanidines from the corresponding isothiouronium salts was controlled by the nucleophilicity of the counterion and influenced by the reaction temperature. Further, a new fast-track access to tetrahydropyrimidin-2-ylamines was developed.