1,2-Methyl shift in the reaction of 4,7-dihydro-4,5-dimethyl-7-phenyl-(1,2,4)-triazolo[1,5-a]pyrimidine with tosyl azide
The reaction of the heterocyclic enamine 1 with tosyl azide (2) leads to the tosylimino derivative 4 of 1,2,4-triazolo[1,5-a]pyrimidine. The extrusion of nitrogen from the primary adduct 3 is followed by a 1,2-shift of a methyl group. The structure determination of 4 is based on 1H and 13C nmr spectra including NOE measurements.
The reaction of amino-imidazoles, -pyrazoles and -triazoles with α,β-unsaturated nitriles
The reactions of α,β-unsaturated nitriles (1, 9, 12) as bielectrophiles with aminoazoles (2, 4, 6) as binu-cleophiles were investigated. Acrylonitrile (1) reacts almost exclusively in a chemoselective Michael-type addition yielding the substituted azoles 3, 5 and 7, respectively. Cinnamonitriles 9a,b behave in a similar way, but the free CN group adds a second molecule 4 yielding 10a,b and its cyclocondensation product 11a,b as minor component. The attempted formation of azolopyrimidines is best achieved by the reaction of the benzylidenemalononitriles 12a - f with 2 or 4. The process is chemo- and regioselective. The structure determinations were based on NMR measurements including DEFT, C…
Synthesis and Tautomerization of 6,7-Dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines.
The condensation of 5-amino-4-phenyl-1,2,3-triazole (1) with chalcones 2a-e or 3-dimethylamino-propiophenone (4f) leads to the 6,7-dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines 3a-f. The equilibrium of 3 and the tautomeric 4,7-dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines 3′ is described.
Tautomerism of Diazepines Fused with Pyrimidine Rings.
The tautomerism of 1,4-diazepines fused with pyrimidine rings was studied by means of nmr spec-troscopy, X-ray analysis and quantum chemical calculations. It was found that in the case of 6,8-diphenyl-pyrimido[4,5-b][1,4]diazepin-4-ols (7a - e) the enamine form is more stable than the diimine form. This result is rationalized with the electron-withdrawing effect of the 4-hydroxypyrimidine ring and with the formation of intermolecular hydrogen bonds. In contrast to 7a - e, the 6,8-diaryl-2,3,4,7-tetrahydro-1,3-dimethyl-1H-pyrimido[4,5-b][1,4]diazepine-2,4-diones (9a, c, f) exist in the diimine form.
ChemInform Abstract: Cyclocondensation of 6-Acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with Hydroxylamine and Hydrazine.
The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.
ChemInform Abstract: 1,2-Methyl Shift in the Reaction of 4,7-Dihydro-4,5-dimethyl-7-phenyl-(1,2,4)-triazolo[1,5-a]pyrimidine with Tosyl Azide.
The reaction of the heterocyclic enamine 1 with tosyl azide (2) leads to the tosylimino derivative 4 of 1,2,4-triazolo[1,5-a]pyrimidine. The extrusion of nitrogen from the primary adduct 3 is followed by a 1,2-shift of a methyl group. The structure determination of 4 is based on 1H and 13C nmr spectra including NOE measurements.
Reactions of 4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines with α,β-unsaturated carbonyl compounds
The reaction of 5,7-diphenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine (1) with α,β-unsaturated carbonyl compounds 2a-f led to the formation of the alkylated heterocycles 3a-f (Figure 1). However, the reaction of 5-methyl-7-phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine (5) with 2a-c yielded under the same conditions the triazolo[5,1-b]quinazolines 6a-c (Figure 3). In this case, the alkylation is followed by a cyclocondensation. The structure elucidation of the products is based on ir, ms, 1H and 13C nmr measurements and on an X-ray diffraction study.
Cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with hydroxylamine and hydrazine
The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.
Cyclecondensation of 3-amino-1,2,4-triazole with substituted methyl cinnamates
The reaction of 3-amino-1,2,4-triazole (1) with substituted methyl cinnamates 2a-h leads selectively to the formation of 7-aryl-6,7-dihydro[1,2,4]triazolo[1,5-a]pyrimidin-5(4H)-ones 3a-h. The structure eluci dation of the products is based on ir, 1H and 13C nmr measurements and X-ray diffraction.