The reaction of bis(1,3-diphenyl-2-imidazolidinylidene) (Ⅰ) with acetophenone gave two products,N,N'-diphenyl-N-(β-benzoylvinyl) ethylenediamine (Ⅲ) and 1,3-diphenyl-2-phenacylimidazolidine (Ⅳ).Their yields depended on experimental conditions and Ⅳ could be converted to Ⅲ on heating.Similarly,the reaction of Ⅰ with cyclohexanone afforded N,N'-diphenyl-N- (a-oxo-cyclohexylidene-methyl) ethylenediamine (Ⅴ) or 1,3-diphenyl-2-(a-oxo-cyclohexyl)imidazolidine (Ⅵ),depending on reaction conditions.1,3-biphenyl-2-benzoyl-imidazolidine (Ⅷ) obtained from reaction of Ⅰ with benzaldehyde could be reduced either by the Meerwein-Ponndorf reaction or by treating with ethanthiol and anhydrous zinc chloride to 1,3-diphenyl-2-benzal-imidazolidine (Ⅸ).In the presence of air or iodine,Ⅸ produced a cationic radical which gave characteristic E S R signal.