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Reaktionen von 3-Dimethylamino-2,2-dimethyl-2H-azirin mit. NH-aciden Heterocyclen; Synthese von 4H-imidazolen

✍ Scribed by Gabriele Mukherjee-Müller; Stanislav Chaloupka; Heinz Heimgartner; Hans Schmid†; Helmut Link; Karl Bernauer; Peter Schönholzer; John J. Daly

Publisher
John Wiley and Sons
Year
1979
Tongue
German
Weight
655 KB
Volume
62
Category
Article
ISSN
0018-019X

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✦ Synopsis

Reactions of 3‐Dimethylamino‐2,2‐dimethyl‐2__H__‐azirine with NH‐Acidic Heterocycles; Synthesis of 4__H__‐Imidazoles

In this paper, reactions of 3‐dimethylamino‐2,2‐dimethyl‐2__H__‐azirine (1) with heterocyclic compounds containing the structure unit CONHCONH are described. 5,5‐Diethylbarbituric acid (5) reacts with 1 in refluxing 2‐propanol to give the 4__H__‐imidazole derivative 6 (Scheme 2) in 80% yield. The structure of 6 has been established by X‐ray crystallography. Under similar conditions 1 and isopropyl uracil‐6‐carboxylate (7) yield the 4__H__‐imidazole 8 (Scheme 3), the structure of which is deduced from spectral data and the degradation reactions shown in Scheme 3. Hydrolysis of 8 with 3N HCl at room temperature leads to the α‐ketoester derivative 9, which in refluxing methanol gives dimethyl oxalate and 5‐dimethyl‐amino‐2,4,4‐trimethyl‐4__H__‐imidazole (10). On hydrolysis the latter is converted to the known 2,4,4‐trimethyl‐2‐imidazolin‐5‐one (11) [6]. Quinazolin‐2,4 (1__H__, 3__H__)‐dione (12) and imidazolidinetrione (parabanic acid, 14) undergo with 1 a similar reaction to give the 4__H__‐imidazoles 13 and 15, respectively (Schemes 4 and 5).

In Scheme 6 two possible mechanisms for the formation of 4__H__‐imidazoles from 1 and heterocycles of type 16 are formulated. The zwitterionic intermediate f corresponds to b in Scheme 1. Instead of dehydration as in the case of the reaction of 1 with phthalohydrazide [3], or ring expansion as with saccharin and cyclic imides [1] [2], f, undergoes ring opening (way A or B). Decarboxylation then leads to the 4__H__‐imidazoles 17.

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## 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-azirine (1) and 5,s-disubstituted hydantoins 4 in MeCN or i-PrOH give 2-(l-aminoalkyl)-5-(dimethylamino)