Ring-Transformation von Imidazolidin-2,4-dionen (= Hydantoinen) zu 4H-Imidazolen bei der Umsetzung mit 3-(Dimethylamino)-2,2-dimethyl-2H-azirin

Abstract

Ring Transformation of Imidazolidine-2,4-diones (= Hydantoins) to 4H-Imidazoles in the Reaction with 3-(Dimethylamino)-2,2-dimethyl-2H-azirines. At ca. 70°, 3-(dimethylamino)-2,2-dimethyl-2H-azirin (1e) 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 sink complexes 12 of the corresponding 2-(1-aminoalkyl)-4H-imidazoles 5 (Scheme 4 ) .