M. G. Kurella

Synthesis and structure of novel derivatives of thieno[2,3-b]thiocine. An unusual product of intramolecular cycloaddition of 2-homomethallylthio-5-methyl-3-thiophenecarbonitrile oxide

Abstract9-Methyl-3,3a,4,5-tetrahydro-6H-thieno[2,3-b]thiocino[4,5-c]isoxazole and 9-hydroxyimino-2-methyl-7-methylene-6, 7,8,9-tetrahydro-5H-thieno[2,3-b]thiocine have been prepared for the first time by the oxidation of 2-ω-alkenylthio-3-thiophenecarbaldoximes with NaOCl. X-ray structural investigations of thieno[2,3-b]thiocine and 2-homomethallylthio-5-methyl-3-thiophenecarbaldoxime have been carried out.

THE MOLECULAR AND CRYSTAL STRUCTURE OF STABLE 5-METHYL-2-METHYLSULFONYL-3-THIOPHENECARBONITRILE OXIDE

A stable thiophene derivative, 5-methyi-2-methylsulfonyl-3-thiophenecarbonitrile oxide, which is active in reactions with dipolarophiles, was studied by means of X-ray structural analysis. In the crystalline state the structure includes two independent molecules with similar values of geometric and conformation parameters. The bond angle at the C atom of the nitrile oxide group is significantly different from 180°. The intramolecular distances between the C and S atoms in the nitrile oxide and sulfonyl groups are well below the equilibrium distance. The stability of the molecule is thought to be increased by electrostatic or donor-acceptor interactions between the atoms of these groups. The mutual orientation of the two independent molecules in the crystal is nearly orthogonal.

Synthesis and X-ray study of a bis-diphenylboron chelate of 3-(diaminomethylene)pentane-2,4-dione

A bis-diphenylboron chelate has been synthesized from 3-(diaminomethylene)pentane-2,4-dione through the action of (butylthio)diphenylborane and its molecular and crystal structures have been determined. The two boron -containing rings have the same six-membered skeleton but differ substantially in conformation and geometric parameters.

Synthesis of derivatives of the new heterocyclic system pyrimido[4′,5′:4,5]pyrimido[1,2-a]benzimidazole

Abstract3-Phenyl-5-methyl(phenyl)-1H,3H-pyrimido[4′,5′:4,5]pyrimido[1,2-a]benzimi-dazole-2,4-diones were obtained by the cyclization of N-phenyl-N′-[3-ethoxycar-bonyl-4-methyl(phenyl)pyrimido [1,2-a]benzimidazol-2-yl]ureas by the action of potassium carbonate. 2-Methyl-5-phenyl-1H-pyrimido[4′,5′:4,5]pyrimido[1,2-a]benzimidazol-4-one was obtained by the reaction of N′-3-ethoxycarbonyl-4-phenylpyrimido[1,2-a]benzimidazol-2-yl]-N,N-dimethylacetamidine with ammonium acetate in ethanol. The synthesized compounds are members of a new heterocyclic system. The molecular and crystal structure of the solvate of 3-phenyl-5-methyl-1H,3H-pyrimido[4′,5′:4,5] pyrimido[1,2-a]benzimidazole-2,4-dione with two molecules of DMF was studied by x-ray crystallographic analysis.

Cycloaddition of α-dialkylborylamino-n-heterocycles to cyanamides

Abstractα-Diisopropylaminopyridine and 2-dipropylborylamino-1-methylbenzimidazole react with cyanamides to give chelate [4+2]-cycloadducts. X-ray crystallography has been used to establish the molecular and crystal structure of the product of the reaction of α-diisopropylaminopyridine and benzoylcyanamide.

Structures of boron chelates of mono- and diacylketene aminals

The molecular and crystal structures of diphenylboron chelates of acetylketeneN-benzoylaminal and 2-(N-benzoyl)diaminomethylene-4-dimethylaminomethylenecyclohexane-1,3-dione and the structure of the difluoroboron complex of diacetylketeneN-benzoylaminal were established. It was found that the aminovinylcarbonyl fragment of the ligand is involved in the formation of a boron-containing ring. A delocalized π-electron system over the NCCCO fragment of the chelate ring is characteristic of the molecules studied both in crystals and solutions.

Conformational peculiarities of a new heterocyclic dihydrothienothiopyranoisoxazole system

The crystalline and molecular structures of 3H-3a,4-dihydro-7-methylthieno[3′,2′:5,6]thiopyrano[4,3-c]isoxazole and 3H-3a,4-dihydro-3-isopropoxycarbonyl-3a,7-dimethylthieno[3′,2′:5,6]thiopyrano[4,3-c]isoxazole are determined by X-ray analysis. The effect of steric factors on intramolecular 1,3-dipolar cycloaddition is shown.

Structure and conformational features of tetrahydrothienothiepinoisoxazole as a novel heterocyclic system

The crystal and molecular structure of a novel heterocyclic system, 8-methyl-3,3a,4,5-tetrahydrothieno[3′,2:6,7]thiepino[4,5-c]isoxazole, has been determined by X-ray analysis. The seven-membered ring has the boat conformation (B), while the isoxazoline cycle has the flat chair conformation (3E). There are strong steric strains between the vicinal protons at the C(3a), C(3), and C(4) atoms.

Some features of the crystal and molecular structure of N-(1,2,4-triazol-5-yl)benzamidine and its hydrochloride

The crystal and molecular structures of N-(1,2,4-triazol-5-yl)benzamidine (1) and its hydrochloride (2) were determined by x-ray crystallography. In compound 1 both independent molecules are Z isomers of the anidine substituted in the imino group and 5-substituted 1H-1,2,4-triazoles. In the crystal the molecules of compound 1 are linked into a stable dimer by intermolecular hydrogen bonds. An undissociated HCl molecule was unexpectedly found in the structure of compound 2, while the structure of the base corresponded to the Z isomer of the amidine substituted in the amino group and to 2H-1,2,4-triazole substituted at position 5. The structures of compounds 1 and 2 are stabilized by an intramolecular hydrogen bond. The HCl molecule participates in the formation of intermolecular hydrogen bonds in compound 2.

Crystal and molecular structure of 7-phenyl-1,2,4-triazolo[1,5-a]-1,3,5-triazine

The crystal and molecular structure of 7-phenyl-1,2,4-triazolo[1,5-a]-1,3,5-triazine were determined. It was shown that the amine nitrogen atom (N1) of the triazole ring acts as a nucleophilic center in the cyclization of N-(1,2,4-triazol-5-yl)amidines with electrophilic reagents.