Reaction of N-vinylpyrazolium and N-vinylindazolium salts with cyanide ion: formation of 1,2-dihydropyrimidines, 3,4-dihydroquinazolines, and quinolines (original) (raw)
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Novel route for the transformation of a pyrimidine ring using hydrazides
Chemistry of Heterocyclic Compounds, 2006
It has been shown from X-ray structural analytical data that the reaction of 2-ethoxycarbonylmethyl-1,4,6-trimethylpyrimidinium iodide with carboxylic acid hydrazides gives pyrazolo [1,5-a]pyrimidine derivatives and not the isomeric triazolo [4,3-a]pyridines previously reported. This novel and previously unreported rearrangement of 1,2-dialkylpyrimidinium salts occurs via recyclization of the pyrimidine ring with inclusion of a fragment of the nucleophilic reagent into the transformation product.
Proceedings of The 12th International Electronic Conference on Synthetic Organic Chemistry
The cyclocondensation reaction of N-(4-methyl-6-oxo-1,6-dihydropyrimidin-2-yl)guanidine with benzaldehyde was found to result in the formation of 2-amino-4-phenyl-4,6-dihydro-1(3)(9)H-pyrimido[1,2a][1,3,5]triazin-6-one. The reaction proceeded chemo-and regioselectively affording the 1,3,5-triazine ring closure at nitrogen atom adjacent to carbonyl group. The structure of 2-amino-4-phenyl-4,6-dihydro-1(3)(9)H-pyrimido[1,2-a][1,3,5]triazin-6-one was supported by 1 H, 13 C NMR and 2D NOESY spectral data. From the experimental data, 3H-tautomeric form seemed to be predominant in DMSO-d 6 solution. The relative energies of the tautomers were estimated using calculations at different levels of theory (HF/6-311G**, B3LYP/6-311++G** and MP2/6-311++G**). Both the experimental and theoretical results excluded 6-hydroxy tautomer from the equilibrium. 2-Amino-4-phenyl-4,6-dihydro-1H-pyrimido[1,2a][1,3,5]triazin-6-one was calculated to be the energetically preferred tautomeric form in gas phase.
Journal of Organic and Pharmaceutical Chemistry, 2015
The peculiarities of the reaction between 3-(2-aminophenyl)-6-R-1,2,4-triazin-5(2H)-ones and cyclic anhydrides of non-symmetric (2-methylsuccinic, 2-phenylsuccinic and camphoric) acids have been described in the present article. The influence of electronic and steric effects of substituents in the anhydride molecule on cyclisation processes has been discussed. The results have shown that the interaction of 3-(2-aminophenyl)-6-R-1,2,4-triazin-5(2H)-ones mentioned above with 2-methylsuccinic and 2-phenylsuccinic acid anhydrides proceeded non-selectively and yielded the mixtures of 2-R 1-3-(2-oxo-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-6-yl)propanoic acids and 1-(2-(5-oxo-6-R-2,5-dihydro-1,2,4-triazin-3-yl)phenyl)-3-R 1-pyrrolidine-2,5-diones. It has been found that low regioselectivity of the acylation process may be explained by insignificant electronic effects of substituents (of the methyl and phenyl fragment) in position 2 of the anhydride molecule on the electrophilic reaction centre. It has been also determined that the reaction between 3-(2-aminophenyl)-6-R-1,2,4-triazin-5(2H)-ones and camphoric anhydride proceeds regioselectively and yielded 1,2,2-trimethyl-3-(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazolin-6-yl)cyclopentan-1-carboxylic acids. Regioselectivity of the interaction mentioned above may be explained by the steric effect of the methyl group. Identity of compounds has been proven by LC-MS, the structure has been determined via a set of characteristic signals in 1 Н NMR, 13 С NMR spectra and position of cross peaks in the correlation HSQC-experiment. Mass spectra of the compounds synthesized have been also studied, the principal directions of the molecule fragmentation have been described. The structure of 1,2,2-trimethyl-3-(3-methyl-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazolin-6-yl)cyclopentane-1-carboxylic acid has been proven by X-ray analysis.
Crystals, 2021
Triazolopyridines are a family of compounds that, owing to their biological activity, have many pharmaceutical applications. In this study, 3-(pyridine-4-yl)-[1,2,4]triazolo[4,3-a]pyridine and 6-bromo-3-(pyridine-4-yl)-[1,2,4]triazolo[4,3-a]pyridine were synthesized by using the chlorinated agent NCS for hydrazones under very mild conditions. The characterization of these compounds was achieved by 1H NMR, 13C NMR, FTIR, MS and X-ray diffraction. The compound 3-(pyridine-4-yl)-[1,2,4]triazolo[4,3-a]pyridine was crystallized in the monoclinic space group P 21/c with a = 15.1413(12), b = 6.9179(4), c = 13.0938(8) Å, β = 105.102(6)°, V = 1324.16(16)Å3, Z = 4, and R = 0.0337. Also compound 6-bromo-3-(pyridine-4-yl)-[1,2,4]triazolo[4,3-a]pyridine was crystallized in the monoclinic space group P 21/c with a = 14.3213(11), b = 6.9452(4) (4), c = 12.6860(8)Å, β = 100.265(6)°, V = 1241.62(14)Å3, Z = 4, and R = 0.0561.
Chlorocadmate(II) salts of two 1,2,4-triazolo-[1,5-a]pyrimidine derivatives
2008
The crystal structure of the ionic compounds (tpH) n [Cd n Cl 3n ] and (dmtpH) 2 [CdCl 4 ] AE 2H 2 O is described, where tp = 1,2,4-triazolo-[1,5-a]pyrimidine and dmtp = 5,7-dimethyl-1,2,4-triazolo-[1,5-a]pyrimidine. Both compounds are monoclinic, space groups P2 1 /c and C2/c, respectively. Unit cell parameters are a = 13.7860(7), b = 9.4013(5), c = 17.6679(9) Å , b = 98.672(1)°for the first compound and a = 11.7543(7), b = 12.6823 , c = 6.6836(4) Å , b = 96.710(1)°for the second. In both cases, the heterocycles are protonated at the nitrogen atom at position 3. For dmtp, the charge of the cation is neutralized by the simple tetrahedral [CdCl 4 ] 2À anion, whereas for tp, a polymeric [Cd n Cl 3n ] nÀ anion is present, formed by aligned face-sharing CdCl 6 octahedra.
Cyclopenta[ b ]pyrroles from Triazines: Synthetic and Mechanistic Studies �
Org Lett, 2010
The pyrrolidine-mediated reactions of 3,5-disubstituted 1,2,4-triazines with cyclobutanone lead to cyclopenta[b]pyrroles, which can be derivatized into hydrazones and oximes. The cyclopenta[b]pyrrole ring system likely arises through a tandem [4 + 2] cycloaddition/cycloreversion/ring rearrangement reaction. In contrast, 3,6-disubstituted 1,2,4-triazines undergo a simple nucleophilic 1,4-addition with cyclobutanone to give 1:1 adducts. An important synthetic application of substituted 1,2,4triazines is their reaction as azadienes in inverse electron demand Diels-Alder reactions to generate substituted pyridines. 1,2 Analogously, 1,2,4,5-tetrazines are known to react with electron-rich enes to give substituted pyridazines. 3 However, in previous work from our laboratory, we did not obtain the expected pyridazine derivative 5 by the reaction of tetrazine 3 with cyclobutanone enolate 2. 4-6 Rather, instead of intermediate 4 eliminating water to aromatize (f 5), diazocinone 6 was obtained through a ring-expansion reaction (Scheme 1). 4,5 Attempts to extend this reaction to produce an eightmembered heterocycle containing a sulfur and two nitrogen atoms by reacting 3 with thietanone 7 and base (Scheme 1)