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

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‐2 H ‐azirine ( 1 ) and 5,5‐disubstituted hydantoins 4 in MeCN or i‐PrOH give 2‐(1‐aminoalkyl)‐5‐(dimethylamino)‐4,4‐dimethyl‐4 H ‐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 CONHCONH 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)‐4 H ‐imidazoles 5 ( Scheme 4 ).