Polyfunctional Pyrazoles. 10*. Synthesis of 5-OXO-4,5,7,9-Tetrahydropyrazolo[3,4-е][1,2,3]-Triazolo[1,5-а][1,3]Diazepine-3-Carboxamides in a Tandem Reaction of Ethyl 4-(Azido-Methyl)Pyrazole-3-Carboxylates with Cyanoacetamides

Abstract

Tandem reactions are an effective tool in modern organic synthesis that has been successfully used to construct a variety of acyclic, carbo-and heterocyclic systems [2][3][4][5][6]. In the field of heterocyclic compound chemistry, for instance, tandem condensation of alkyl 2-azidobenzoates with activated acetonitriles is a basis for efficient synthesis of [1,2,3]triazolo[1,5-a]quinazoline derivatives [7-9], such as the known selective serotonin 5-HT 6 receptor antagonists [7] and inhibitors of the biosynthesis of teichoic acid, a component of the cell wall of many gram-positive bacteria [9]. Among the azidobenzoate pyrazole analogs such transformations are described only for ethyl 5-azido-1-methyl-4-pyrazolecarboxylate, reaction of which with activated nitriles gave 3-substituted pyrazolo[4,3-e][1,2,3]triazolo[1,5-a]pyrimidines [10]. To us it seemed worthwhile to exploit the synthetic potential of tandem reactions of other pyrazole functional derivatives with cyanoacetic acid amides to obtain new condensed heterocyclic compounds.In this work, 4-(azidomethyl)pyrazole-3-carboxylic acid esters 2a-c, formed in essentially quantitative yields by reacting 4-chloromethylpyrazole-3-carboxylic acid ethyl ester 1a-c [11] with sodium azide in DMF solution at 50°C, were studied as potential substrates for tandem condensation reactions. A characteristic of