S. V. Lindeman

Three component condensation of 3-amino-1,2,4-triazole with carbonyl compounds. A new synthesis of 1,2,4-triazolo[1,5-a]pyrimidines

Three component condensation of 3-amino-1,2,4-triazole with an aromatic aldehyde and ketone gives 1,2,4-triazolo[1,5-a]-pyrimidines. An x-ray structural investigation of 5-phenyl-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]benzo[h]quinazoline was undertaken in order to determine the course of this reaction.

Imine-enamine tautomerism of dihydroazolopyrimidines. 3. 5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines

Abstract5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines were obtained by condensation of 3-amino-1,2,4-triazole with Β-dimethylaminopropiophenone hydrochlorides or crotophenone. The effect of steric and electronic factors on the position of the imine-enamine equilibrium in solutions of the synthesized substances is examined. 5-Phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyriniidine was subjected to x-ray diffraction analysis.

Synthesis and structure of 3-oxopyrano[3,4-c]pyridines

Acylation of the enamine of 2,2-dimethyltetrahydropyran-4-one with acid chlorides produced α-acylpyran-4-ones which give 3-oxopyrano[3,4-c]pyridines when treated with cyanoacetamide.

1β,10α-Dihydroxyarglabin — A new sesquiterpene lactone fromArtemisia glabella

The new sesquiterpene lactone 1β,10α-dihydroxydihydroxyarglabin has been isolated from the epigeal part ofArtemisia glabella Kar. et Kir., and its structure has been established on the basis of spectral characteristics, independent synthesis, arglabin, and an x-ray structural investigation.

Reactions at the double bond in the epoxy group of arglabin

The interaction of arglabin, a sesquiterpene lactone of the guainane type, with peracetic acid and hydrogen chloride has been investigated. This led to the synthesis of nine compounds the structure of which have been established in the basis of spectral characteristics (IR, PMR, and mass spectra). The structures and absolute configurations of the molecules of 3α,10α-dichloro-1β,4β-dihydroxy-and 10α-chloro-1β-hydroxy-3β,4β-epoxyarglabins have been determined as 3R, 10R-dichloro-1R,4R-dihydroxy-5S,6S,7S-trans-trans-guai-11(13)-en-6,12-olide and 10R-chloro-1R-hydroxy-3S,4R-epoxy-5S,6S,7S-trans-trans-guai-11(13)-en-6,12-olide, respectively.

Nontrivial Intramolecular Interaction in Ozonation of Dimethyl Ester of endo,cis-bicyclo[2,2,1]hept-5-en-2,3-dicarbonic acid in diethyl ether

Abstract The formation of the product of intramolecular interaction of a zwitterion and a methoxycarbonyl group was observed in the process of ozonating dimethyl ester of endo,cis-bicyclo [2,2,1]hept-5-en-2,3-dicarbonic acid in diethyl ether. The structure of racemic endo,cis-4-methoxy-5-methoxycarbonyl-6-formyl-1,4-epoxy-2,3-dioxacyclopenta[2,3-δ] cyclohexane was established by an X-ray structure analysis.

Imine-enamine tautomerism of dihydroazolopyrimidines 5. Steric effects and the tautomeric equilibrium for dihydro-1,2,4-triazolo[1,5-a]pyrimidines

The reaction of 3-amino-1,2,4-triazole with β-dimethylaminopropiophenones or unsaturated ketones gives 5,7-disubstituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines. An increase in the bulk of the substituent at C(7) in the bicyclic system leads to relative stabilization of the enamine tautomer of these compounds. An x-ray diffraction structural analysis of 7-tert-butyl-5-(4-methoxyphenyl)-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine showed that the introduction of a tert-butyl group into the dihydropyrimidine ring leads to significant loss of planarity of this system.

X-ray crystallographic and quantum-chemical investigation of tert-butyl hydroperoxide

An MNDO calculation and an x-ray crystallographic investigation of tert-butyl hydroperoxide (I) were undertaken. The two symmetrically independent molecules of (I), which in fact have identical geometric parameters, form infinite chains along the y axis through staggered hydrogen bonds. The chains have local symmetry, described by a noncrystallographic slip plane. The difference between the experimental value of the COOH dihedral angle (average 100°) and the calculated value (128.5°) is most likely due to the formation of intermolecular hydrogen bonds in the crystal, the energies of which (∿30 kJ/mole) are considerably larger than the calculated excess energy of the conformers observed in the crystal (3.4 and 1.9 kJ/ mole).

Synthesis, and crystal and molecular structures of anabasinium O,O-dialkyl phosphorothioates

The synthesis has been effected of anabasinium O,O-dialkyl phosphorothioates. The crystal and molecular structures of the complex compounds obtained have been determined by the method of x-ray structural analysis. It has been established that the cations and anions of the anabasinium O,O-dialkyl phosphorothioates are combined into cyclic associates each including two anions and two cations with different conformations.

Molecular and crystal structure of the germacranolides salonitenolide and hanphyllin

A sesquiterpene lactone of the germacrane type, salonitenolide, has been isolated for the first time from the epigeal part ofCentaurea pseudomaculosa Dobrocz (spotted centaurea) and has been identified. The structures of the germacranolides and hanphyllin have been determined by the method of x-ray structural analysis: salonitenolide is 8-hydroxy-6β,8β(H)7α(H)-germacra-1(10),4,11(13)-trien-6,12-olide and hanphyllin is 3-hydroxy-3α,7α(H),6β(H)-germacra-1(10),4,11(13)-trien-6,12-olide. It has been established that the ten-membered rings of salonitenolide and hanphyllin are of the chair-chair type,1D14,15D5. On the basis of the results of CD spectroscopy, the chiral centers in the hanphyllin molecule have been assigned the 3S, 6R, and 7S configurations.