ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Reactions of 3-Dimethylamino-2,2-dimethyl-2H-azirine with NH-Acidic Heterocycles; Synthesis of 4H-ImidazolesIn this paper, reactions of 3-dimethylamino-2,2-dimethyl-2H-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 4H-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 4H-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-4H-imidazole (10). On hydrolysis the latter is converted to the known 2,4,4-trimethyl-2-imidazolin-5-one (11) [6]. Quinazolin-2,4 (1H, 3H)-dione (12) and imidazolidinetrione (parabanic acid, 14) undergo with 1 a similar reaction to give the 4H-imidazoles 13 and 15, respectively (Schemes 4 and 5).In Scheme 6 two possible mechanisms for the formation of 4H-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 4H-imidazoles 17.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19790620314
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