Ring-Transformation of Imidazolidine-2,4-diones ( = Hydantoins ) to 4H-Imidazoles in the Reaction with 3-(Dimethylamino)-2,2-dimethyl-2H-azirines

Article abstract of DOI:10.1002/hlca.19920750425

At ca. 70 deg C, 3-(dimethylamino)-2,2-dimethyl-2H-azirine (1) and 5,5-disubstituted hydantoins 4 in MeCN or i-PrOH give 2-(1-aminoalkyl)-5-(dimethylamino)-4,4-dimethyl-4H-imidazoles 5 in good yield (Scheme 2).These products are decarboxylated 1:1 adducts of 1 and 4.A reaction mechanism is suggested in analogy to the previously reported reactions of 1 and NH-acidic heterocycles containing the CO-NH-CO-NH moiety (Scheme 5).The formation of ureas 6 and 7 can be rationalized by trapping the intermediate isocyanate F by an amine.No reaction is observed between 1 and 1,5,5- or 3,5,5-trisubstituted hydantoins in refluxing MeCN or i-PrOH, but an N-isopropylation of 1,5,5-trimethylhydantoin (8b) occurs in the presence of morpholine (Scheme 3).The reaction of the bis(azirine)dibromozink complex 11 and hydantoines 4 in refluxing MeCN yields zink complexes 12 of the corresponding 2-(1-aminoalkyl)-4H-imidazoles 5 (Scheme 4).