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Umsetzungen von 3-(Dimethylamino)-2,2-dimethyl-2H-azirim mit Barbitursäure-Derivaten


Schläpfer-Dähler, Marlise; Heimgartner, Heinz (1990). Umsetzungen von 3-(Dimethylamino)-2,2-dimethyl-2H-azirim mit Barbitursäure-Derivaten. Helvetica Chimica Acta, 73(8):2275-2286.

Abstract

The reaction of 3-(dimethylamino)-2,2-dimethyl-2H-azirine (1) and 5,5-disubstituted barbituric acids 5 in i-PrOH at ca. 70° gives 2-[5-(dimethylamino)-4,4-dimethyl-4H-imidazol-2-y1]alkanamides of type 6 in good yields (Scheme 1). The formation of 6 proceeds with loss of CO2; various reaction mechanisms with a zwitterionic 1:1 adduct B as common intermediate are discussed (Schemes 2 and 5). Thermolysis of product 6 leads to 2-alkyl-5-(dimethylamino)-4,4-dimethyl-4H-imidazoles 8 or the tautomeric 2-alkylidene derivatives 8' via elimination of HNCO (Scheme 3). The latter undergoes trimerization to give 1,3,5-triazine-2,4,6-trione. No reaction is observed with 1,5,5-trisubstituted barbiturates and 1 in refluxing i-PrOH, but an N-alkylation of the barbiturate occurs in the presence of morpholine (Scheme 4). This astonishing reaction is explained by a mechanism via formation of the 2-alkoxy-2-(dimethylamino)aziridinium ion H which undergoes ring opening to give the O-alkylated 2-amino-N',N'- dimethylisobutyramide I as alkylating reagent (Scheme 4).

The reaction of 3-(dimethylamino)-2,2-dimethyl-2H-azirine (1) and 5,5-disubstituted barbituric acids 5 in i-PrOH at ca. 70° gives 2-[5-(dimethylamino)-4,4-dimethyl-4H-imidazol-2-y1]alkanamides of type 6 in good yields (Scheme 1). The formation of 6 proceeds with loss of CO2; various reaction mechanisms with a zwitterionic 1:1 adduct B as common intermediate are discussed (Schemes 2 and 5). Thermolysis of product 6 leads to 2-alkyl-5-(dimethylamino)-4,4-dimethyl-4H-imidazoles 8 or the tautomeric 2-alkylidene derivatives 8' via elimination of HNCO (Scheme 3). The latter undergoes trimerization to give 1,3,5-triazine-2,4,6-trione. No reaction is observed with 1,5,5-trisubstituted barbiturates and 1 in refluxing i-PrOH, but an N-alkylation of the barbiturate occurs in the presence of morpholine (Scheme 4). This astonishing reaction is explained by a mechanism via formation of the 2-alkoxy-2-(dimethylamino)aziridinium ion H which undergoes ring opening to give the O-alkylated 2-amino-N',N'- dimethylisobutyramide I as alkylating reagent (Scheme 4).

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Additional indexing

Other titles:Reactions of 3-(Dimethylamino)-2,2-dimethyl-2H-azirine with Barbituric-Acid Derivatives
Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:German
Date:1990
Deposited On:27 Mar 2014 10:51
Last Modified:05 Apr 2016 17:46
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung, F. Hoffmann-La Roche AG, Basel
Publisher DOI:https://doi.org/10.1002/hlca.19900730824
Permanent URL: https://doi.org/10.5167/uzh-94219

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