Formylation of 4,7‐Dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidines Using Vilsmeier–Haack Conditions

Formylation of 5‐methyl‐7‐phenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine 1a using Vilsmeier–Haack conditions yields 5‐methyl‐7‐phenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidin‐6‐ylcarbaldehyde 3a . 5,7‐Diaryl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidines 1b , 1c in this reaction apart from formylation undergo recyclization into 5‐aryl‐1,2,4‐triazolo[1,5‐a]pyrimidin‐6‐ylmethane derivatives 4b , 4c , 5b , 5c , and 6 . The structure of the synthesized compounds was determined on the basis of NMR, IR, and MS spectroscopic data and confirmed by the X‐ray analysis of the 6‐(ethoxy‐phenyl‐methyl)‐5‐phenyl‐[1,2,4]triazolo[1,5‐a]pyrimidine 6 , 5‐phenyl‐6‐(1‐phenyl‐vinyl)‐[1,2,4]triazolo[1,5‐a]pyrimidine 11 , and 7‐phenyl‐6‐(1‐phenyl‐vinyl)‐[1,2,4]triazolo[4,3‐a]pyrimidine 12 .     

Electronic effects of substituents on the conformational characteristics of the 1,2-dihydropyridine ring

The electronic effects of substituents on the conformational characteristics of the 1,2-dihydropyridine ring were investigated by the MP2/6-31G(d) quantum chemical method. Introduction of a nitro group leads to a flattening of the ring; on the potential energy surface, the minimum corresponding to the conformer with an axial orientation of the NH hydrogen atom vanishes. An opposite tendency is observed in amino derivatives. Intramolecular interactions are analyzed to see how they affect the the equilibrium geometry and the energy characteristics of the dihydroheterocycle.Original Russian Text Copyright © 2004 O. V. Shishkin and R. I. ZubatyukTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 589–594, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Molecular and crystal structures of some novel derivatives of 3-aryl-7-arylidene-3,3<Emphasis Type="Italic">a</Emphasis>,4,5,6,7-hexahydroindazoles

The stereochemical aspects of the interaction of 2,6-bis(arylidene)-cyclohexanone and 2,6-bis(arylidene)-3-methylcyclohexanone with arylhydrazine (aryl is phenyl or 4-nitrophenyl) and methylhydrazine are investigated using X-ray diffraction analysis. The molecular structure of the 3-aryl-7-arylidene-3,3a,4,5,6,7-hexahydroindazoles synthesized is determined by X-ray diffraction analysis for the first time. It is established that the stereochemistry of the products of the interaction between the cyclohexanone derivatives and arylhydrazines depends on the electronic nature of the substituent in the aryl group. Two regioisomeric products with different positions of the methyl group in the cyclohexane ring with respect to the arylidene fragment are synthesized by the reaction of 2,6-bis(4-methoxybenzylidene)-3-methylcyclohexanone with methylhydrazine. The influence of the substituents at the nitrogen atom of the pyrazoline ring on the intramolecular electronic interactions and the geometry of the heterocycle in the compounds under investigation is discussed.     

Germanium(IV) bischelates with 2-hydroxynaphthaldehyde pyridinoylhydrazones: The crystal and molecular structure of the complex with isonicotinoylhydrazone (H<Subscript>2</Subscript>Inf), [Ge(Inf · HCl)<Subscript>2</Subscript>] · 5H<Subscript>2</Subscript>O

The reactions of GeCl₄ with 2-hydroxynaphthaldehyde pyridinoylhydrazones (H₂L) in methanol give complexes [Ge(L · HCl)₂] · nH₂O. The data of mass spectrometry, thermogravimetry, and IR and ¹H NMR spectroscopy indicate that the ligand molecules are protonated at the pyridine nitrogen atom with hydrogen chloride and coordinated to germanium in the tridentate mode through the azomethine nitrogen atom and the oxyazine and oxy group oxygen atoms. The structure of the complex with isonicotinoylhydrazone (H₂Inf), [Ge(Inf · HCl)₂] · 5H₂O has been determined by X-ray diffraction