Roads to new guanidine chemistry from 2-imidazolidinones through 2-chloroamidinium derivatives

New guanidine chemistry from 2-imidazolidinones through 2-chloroamidinium derivatives is introduced. At first the synthetic utility of 2-cloro-1,3-dimethylimidazolinium chloride (DMC), derived from 1,3-dimethylimidazolidinone, mainly focusing on dehydration, is discussed. Modified guanidines and guanidinium salts can be prepared from DMC and its analogs by aminations with primary and secondary amines, respectively. The roles of modified guanidines not only chiral auxiliaries in asymmetric synthesis but also the nitrogen source of aziridine skeletons in guanidinium ylide-participating aziridine synthesis are discussed.