Faculty of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan, and Central Research Laboratory, Shiratori Pharmaceutical Co. Ltd., 6-11-24 Tsudanuma, Narashino, Chiba 275-0016, Japan.
Modified guanidines were explored as potential chiral superbases. Thus, chiral 1,3-dimethyl-2-iminoimidazolidines with or without 4, 5-diphenyl groups, their guanidinium salts, and the 2-iminoimidazolidines with (S)-1-phenylethyl groups on the ring nitrogens were prepared by treatment of 2-chloroimidazolinium chlorides with appropriate amines. Bicyclic guanidines were also prepared from a prolinamide using a similar procedure.