Structure of 2-Methyl-5,6,7-triphenyl-6,7-dihydropyrazolo[2,3-\u3cem\u3ea\u3c/em\u3e]pyrimidine

C25H21N3, Mr = 363.46, monoclinic, P21/n, a = 9.245 (2), b = 23.502 (5), c = 9.340 (2) Å, β= 103.50(3)°, V=1973.3(2) Å3, Z=4, Dx= 1.220 (2) g cm-3, λ (Mo Kα )= 0.71069 Å, μ = 0.068 cm-1, F(000) = 768, T= 292 K, R = 0.091 for 1442 unique observed reflections. The dihydropyrimidine ring adopts a distorted sofa conformation. The aryl substituents on the saturated C atoms have an axial orientation

Doebner-type pyrazolopyridine carboxylic acids in an Ugi four-component reaction

Substituted 1H-pyrazolo[3,4-b]pyridine-4- and 1H-pyrazolo[3,4-b]pyridine-6-carboxamides have been synthetized through a Doebner–Ugi multicomponent reaction sequence in a convergent and versatile manner using diversity generation strategies: combination of two multicomponent reactions and conditions-based divergence strategy. The target products contain as pharmacophores pyrazolopyridine and peptidomimetic moieties with four points of diversity introduced from readily available starting materials including scaffold diversity. A small focused compound library of 23 Ugi products was created and screened for antibacterial activity

The Effect of Substituents on the Conformational Mobility of the Heterocycle in 1,4-Dihydropyrimidine and its Derivatives

The equilibrium geometry of 1,4-dihydropyrimidine, 4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine, and their alkyl (Me, Et, Pri, But) and phenyl derivatives has been calculated by molecular mechanics method. The equilibrium conformation of unsubstituted molecules is planar, but it is easily transformed to the boat conformation with a small change in the conformational energy. The effect of substituents on the geometry and conformational mobility of the dihydropyrimidine ring has been studied

Conformational Analysis of 3,4-Dihydropyridine and its Alkyl Derivatives

The geometry of dihydropyridine and its alkyl derivatives was studied by the molecular mechanics method. The dihydrocycle was found to be mobile; however, substituents exert little effect on its distorted sofa conformation. The alkyl groups attached to the saturated carbon atoms occupy pseudo-equatorial position in monosubstituted and pseudo-axial positions in disubstituted 3,4-dihydropyridines. Unusually high barriers to inversion of the dihydrocycle were observed incis-3,4-dialkyl-3,4-dihydropyridines caused by the eclipse of the substituents in the transition state

Features of the behavior of 4-amino-5-carboxamido-1,2,3-triazole in multicomponent heterocyclizations with carbonyl compounds

Multicomponent reactions involving polyfunctional 4-amino-5-carboxamido-1,2,3-triazole and cyclic carbonyl-containing CH-acids were studied under conventional thermal heating, microwave and ultrasonic irradiation. The features of the reactions studied were discussed and the optimized procedures for the synthesis of final triazolopyrimidines were elaborated. In contrast to the similar MCRs of numerous other aminoazoles, a change of direction of the heterocyclizations in the case of 4-amino-5-carboxamido-1,2,3-triazole was not observed when microwave or thermal heating was substituted by ultrasonication at ambient temperature

Conformational Analysis of 5,6-dihydropyrimidine and Its Derivatives

The equilibrium geometry and inversion barriers of 5,6-dihydropyrimidine, 6,7-dihydroazolopyrimidines with node nitrogen atoms and their alkyl (Me, Et, Pri, But) and phenyl derivatives were calculated using a molecular mechanics approach. Annelation with azole cycles and the introduction of substituents have a slight effect on the equilibrium conformation of the dihydrocycle (distorted sofa). Alkyl substutuents at saturated carbons have an essentially equatorial orientation in 5,6-dihydropyridimine derivatives and are axial in the annelated analogs. On the other hand, the equatorial conformers are more stable in phenyl derivatives of dihydroazolopyrimidines. Factors determining the relative stability of conformers were analyzed

Molecular and Crystal Structure of 5,7-Diphenyl-7-Methyl-4,7-Dihydro-1,2,4-Triazolo[1,5-a]pyrimidine

The molecular and crystal structures of 5,7-diphenyl-7-methyi-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine have been studied by X-ray structural methods. The crystal is monoclinic,a=16.112(3),b=13.489(3),c=14.480(3)Å, β=101.62(2)°,Z=8, space groupC2/c,R=0.071. The presence of short intermolecular contacts indicates considerable steric strain in the molecule. The dihydropyrimidine ring exists in an unevenly planar boat conformation. Increasing the steric strain of the dihydrocycle leads to a twisted conformation

The Effect of the Azole Ring on the Conformational Mobility of the Dihydropyrimidine Ring in 4,7-Dihydroazolo[1,5-\u3cem\u3ea\u3c/em\u3e]Pyrimidines as Judged from MNDO Calculations

The equilibrium geometries of 4,7-dihydropyrazolo[1,5-a]pyrimidine, 4,7-dihydrotetrazolo [1,5-a]pyrimidine, 4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine, and 1,4-di-hydropyrimido [1,2-a]imidazole were calculated by the semiempirical quantum-chemical MNDO method. The dihydropyrimidine ring exhibits high conformational mobility in all of these compounds. The change in the energy occurring in the transition of the molecule to the boat conformation with an angle between the planar fragments of ±20° does not exceed 1 kcal mol−1. The mobility of the dihydro ring increases as interactions between the π-systems of the azole ring and the C=C double bond separated by an imino group and a methylene bridge decrease

Cycle Mobility in 1,4-Dihydropyridine and its Monoalkyl and Phenyl Derivatives

The conformational mobility of the 1,4-dihydropyridine cycle has been studied by the molecular mechanics method. It was shown that the N(1) and C(4) atoms are displaced asymmetrically from the plane of the double bonds. The asymmetry is the result of conjugation between the nitrogen lone pair and the π systems of the double bonds. The influence of alkyl and phenyl substituents at the carbon atoms on the equilibrium conformation and cycle mobility has been investigated