Ph3P/I2-Mediated Synthesis of N,N',N-Substituted Guanidines and 2-Iminoimidazolin-4-ones from Aryl Isothiocyanates

A convenient one-pot procedure for the synthesis of acyclic and cyclic guanidines mediated by the Ph3P/I-2 system is described. Sequential condensation of aryl isothiocyanates with amines followed by dehydrosulfurization and guanylation could lead to both symmetric and unsymmetric N,N',N-substituted derivatives. Through a tandem guanylation-cyclization, a series of 2-iminoimidazolin-4-ones could also be prepared in good yields from the reaction of aryl isothiocyanates with amino acid methyl esters.