Reactions of 5 R 3 amino 1,2,4 triazoles with ethoxymethylideneacetylacetone and ethyl ethoxymethylideneacetoacetate proceeded regioselectively, giving 2 R 7 methyl[1,2,4]triazolo[2,3 a] pyrimidines in good yields. The compounds obtained were characterized by elemental analysis, 1 H NMR spectroscopy, and X ray diffraction analysis (for ethyl 2 ethylthio 7 methyl [1,2,4]triazolo[2,3 a]pyrimidine 6 carboxylate). The frontier orbitals, the molecular electrostatic potential, and the geometries of the reagent molecules were calculated by the DFT method (B3LYP/6 31G**).Condensation of aminoazoles (e.g., 3 amino 1,2,4 tri azole and its derivative 1) with bielectrophiles provides a general route to fused heterocyclic systems. With unsym metrical binucleophiles such as aminoazoles, a regioselectivity problem arises in their reactions with unsymmetrical electrophiles. 1-5 Structures, reactivity, and regioselectivity in reactions of 3 amino 1,2,4 tri azole have been extensively studied by physicochemical, spectroscopic, X ray diffraction, and quantum chemical methods. 1-3,6-13Condensation of 3 amino 1,2,4 triazole with ethyl acetoacetate and its homologs proceeds regioselectively to give triazolopyrimidinones 2, 1,3,14,15 while cycliza tion with unsymmetrical diketones leads to a mixture of regioisomeric triazolopyrimidines 3 and 3´ (Scheme 1). Their relative yields depend on the steric factor. 16 A reaction of aminotriazole and its derivatives with β ethoxymethylidenecarbonyl compounds, which is usu ally carried out in acetic acid, starts with nucleophilic substitution of the ethoxy group 17-19 with participation of the exo amino group of the azole. This is followed by intramolecular cyclization involving the "pyrrole type" ring N atom and ketone carbonyl, ester, or cyano groups (compounds 4-6). In the case of ethyl ethoxymeth ylidenecyanoacetate, chemoselectivity takes place. 20-22 Use of ethoxymethylidenecyanamide for the synthesis of 5 amino[1,2,4]triazolo[2,3 a][1,3,5]triazines (5 aza adenines) 7 is described in Ref. 23.Aminotriazoles can also be involved in three compo nent condensations with aldehydes and active methylene dicarbonyl compounds (dimedone, ethyl acetoacetate, and acetoacetanilides). 2,24-26 These reactions proceed through the formation of an ylidene derivative of the active methylene component, which was proved by an independent synthesis.An attempt to extend the earlier 27 discovered three component condensation with hetarylguanidines, linear β dicarbonyl compounds, and triethyl orthoformate to 3 amino 1,2,4 triazole was unsuccessful. Instead of the expected triazolopyrimidines 8, we isolated products of condensation of compound 1 with the orthoester. Compounds 8 were obtained through the use of ethoxy methylidene derivatives 9 (Scheme 2).In the present work, we studied reactions of 5 R 3 ami no 1,2,4 triazoles with ethoxymethylideneacetylacetone and ethyl ethoxymethylideneacetoacetate by using quan tum chemical molecular calculations, preparatively iso lated the resulting compounds, and examined their...
Fused pyrimidine derivatives R 0515 Novel Variant of Recyclization of N-Arylmaleimides When Reacted with Aminoazoles. -(KOVYGIN, Y. A.; KRYLSKI, D. V.; ZORINA, A. V.; SHIKHALIEV, K. S.; Chem. Heterocycl. Compd. (N. Y.) 40 (2004) 9, 1222-1223; Voronezh State Univ., Voronezh 394693, Russia; Eng.) -H. Toeppel 23-158
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