[4 + 2]-cycloaddition of alkyl vinyl ethers to 3-aroylpyrrolo[1,2-a]quinoxaline-1,2-dione

Russian Journal of Organic Chemistry -     

Electronic structure of 4H-pyrido[1,2-a]pyrimidin-4-ones

The characteristic features of ir and uv spectra of 43 4H-pyrido[1,2-a]pyrimidin-4-one derivatives with electron donor or acceptor groups in position 3, and positions 6, 7, 8, or 9, respectively, have been systematically studied. On the basis of the spectra some conclusions have been drawn for the molecular structure. The negative solvent effect of the lowest-energy π → π* transition is investigated by the PPP method.     

Synthesis of novel imidazo[1,2-a][3,1]benzothiazines 4, imidazo[1,2-a]-[1,2,4]benzotriazines 5, and 4H-imidazo[2,3-c]pyrido[2,3-e][1,4]oxazines 6

Starting from the readily available 2-aminobenzhydrols ( 7 ), 3-amino-1,2,4-benzotriazine ( 11 ) and 2-amino-3-pyridinol ( 12 ), novel derivatives of 5-phenyl-5H-imidazo[1,2-a][3,1]benzothiazine-2-carboxylic acid, ethyl ester ( 4 ), imidazo[2,1-c][1,2,4]benzotriazine-2-carboxylic acid, ethyl ester ( 5 ) and 4H-imidazo[2,3-c]pyrido-[2,3-e][1,4]oxazine ( 6 ) were prepared.     

Tetrahydro- and octahydropyrido[1,2-a]pyrimidin-4-ones

The catalytic hydrogenation of 2-methyl-, 1 2,8-dimethyl-, 2 , 2,9-dimethyl-, 3 , 9-methyl-2-propyl-, 4 , 2,3,9-trimethyl-, 5 , 9-methyl-2-phenyl-, 6 , 9-hydroxy-2-methyl-, 7 , 9-acetoxy-2-methyl, 8 , 9-carboxy-2-methyl-, 16 , 9-carboethoxy-2-methyl-, 17 , 9-carbomethoxy-2-methyl-, 18 , and several 9-carboxamido-2-methyl-, 19, 20 , and 21 , derivatives of the pyrido[1,2-a]pyrimidin-4-one heterocycle has led to a series of novel 6,7,8,9-tetrahydro- and fully saturated, octahydro analogs. In deuteriochloroform or DMSO-d₆ solution, the pmr spectra of the tetrahydro derivatives derived from 1-7 revealed only the 6,7,8,9-tetrahydro structures. In the pmr spectra of 16-21 , there was evidence of a facile 1,3-prototropic shift of the proton from position-9 to position-1, resulting in equilibria between tautomeric species, i.e., . The ratio of tautomers present at equilibrium, with the esters, favored the enamine conformation, whereas, with both the carboxylic acid and the amides, the imine structure predominated. Supportive evidence for the enamine structure with the esters was derived also from the ir spectra. Alkylation of the anion derived from the tetrahydro 9-carbomethoxy derivative with sodium hydride led exclusively to derivatives of 6,7,8,9-tetrahydro system.     

Selective synthesis of bis[1,2]dithiolo[1,4]thiazines from 4-isopropylamino-5-chloro-1,2-dithiole-3-ones

Reaction of 4-isopropylamino-5-chloro-1,2-dithiole-3-ones 3 and S₂Cl₂ in acetonitrile gave selectively 3-oxo-bis[1,2]dithiolo[1,4]thiazine-5-thiones 1 by the addition of triethylamine and bis[1,2]dithiolo[1,4]thiazine-3,5-diones 5 under the action of formic acid. 3,5-Diones 5 were also obtained by intramolecular cyclization of N,N-bis(5-chloro-3-oxo[1,2]dithiol-4-yl)amines 6 with S₂Cl₂ in the presence of Et₃N.     

Derivatives of benzo[4,5]cyclohepta[1,2-b]thiophene. 4. Synthesis of 1-(9,10-dihydro-4H-benzo[4,5]cyclohepta[1,2-b]thiophen-4-yl)-3-alkylaminoazetidines

Thirteen 1-(9,10-dihydro-4H-benzo[4,5]cyclohepta[1,2-b]thiophen-4-yl)-3-alkylaminoazetidines 11 have been synthesized in three steps from 4-amino-9,10-dihydro-4H-benzo[4,5]cyclohepta[1,2-b]thiophene ( 6 ), which was obtained from the reduction of either 4-azido 4 or 4-hydroxyimino 5 derivatives. All the compounds have been evaluated as potential antidepressive agents.     

Biginelli Synthesis of Regioisomeric 5,6-Dihydro-4H-benzo[4,5]imidazo[1,2-a]pyranopyrimidin-4-ones

Russian Journal of Organic Chemistry - A modified version of the three-component Biginelli reaction of 4-hydroxy-6-methyl-2H-pyran-2-one with aromatic aldehydes and 1H-benzimidazol-2-amine has been...     

The stereochemistry of 1,6,7,12b-Tetrahydro-2H,4H-[1,2] oxazino[3′,4′:1,2]-pyrido[3,4-b]indole and of 1,2,3,6,7,12b-Hexahydro-3-methyl-4H-pyrimido[3′,4′:1,2]pyrido[3,4-6] indole

From an analysis of nmr spectral data, 1,6,7,12b-tetrahydro-2H,4H-[1,3 ]oxazino[3′, 4′ :1,2]-pyrido[ 3,4-b ]indole is shown to exist in solution at room temperature almost entirely in the cis-fused ring conformation with the nitrogen lone pair bisecting the C4 methylene group whereas under the same conditions 1,2,3,6,7,12b-hexahydro-3-methyl-4H-pyrimido[3′,4′:1,2] pyrido-[3,4-b ]indole exists as an approximately 50:50 equilibrium mixture of the cis and trans-fused ring conformations.     

Synthesis of 4-Aryl Benzimidazolo[1,2-a]-s-triazin-2-ones and 2-Aroylaminobenzimidazolo[1,2-b]-1,2,4-thiadiazolines

Reaction of 2-aminobenzimidazole with aroylisothiocyanates gave 2-aroylaminobenzimidazoles ( 3 ) and N-aroyl-N′-(benzimidazol-2-yl)-thioureas ( 4 ). The products obtained on reaction of 4 with PCl₅ in POCl₃, and with oxidising agents have been identified as 4-arylbenzimidazolo[1,2-a]-s-triazin-2-ones ( 5 ) and 2-aroylamino-benzimidazolo[1,2-b]-1,2,4-thiadiazolines ( 7 ) respectively.     

New access to 4-phenyl-6H-pyrrolo[1,2-a]thieno[3,2-f]-[1,4]diazepines

Pyrrolo[1,2-a]thieno[3,2-f][1,4]diazepines were obtained in an original one step synthesis by treatment of imines 1 with paraformaldehyde in refluxing ethanol. The intermediate Mannich bases were also converted into the thienooxadiazocines 12 and the diazepine N-oxide 13 .     

Pyrrolo[1,2-d]triazines-1,2,4. II. Etude des pyrrolo[1,2-d]triazinones-1 et -4

The synthesis of 1,2-dihydro-1-oxopyrrolo[1,2-d]-1,2,4-triazines was achieved by rearrangement of 2-pyrrolyloxadiazoles under alkaline conditions or by cyclisation of pyrrole N-ethoxymethylidene hydrazides. The cyclisation of the N-carbethoxy hydrazone of the pyrrole-2-carboxaldehyde gave the 3,4-dihydro-4-oxopyrrolo[1,2-d]-1,2,4-triazine. Electrophilic substitution reactions of the 1- and 4-pyrrolotriazinones were made either on the lactam nitrogen with methyl sulphate, benzyl chloride and monochloroacetic acid or on the pyrrole ring with bromine and nitric acid. The structure of the derivatives was determined by ¹H nmr.     

Polycyclic systems: Synthesis of isoindolo[2,1-b]-pyrrolo[1,2-d][2,4]benzodiazocine and isoindolo-[1,2-d]pyrrolo[1,2-a] [1,5]benzodiazocine

The synthesis of isoindolo[2,1-b]pyrrolo[1,2-d][2,4]benzodiazocine 7 and isoindolo[1,2-d]pyrrolo[1,2-a]-[1,5]benzodiazocine 13 are described starting from 2-(2-methoxycarbonyl)benzylphthalimide 1a and ethyl α-bromohomophthalate 9 respectively.     

First synthesis of 4H-furo[3,2-f]pyrrolo[1,2-a][1,4]diazepines

The synthetic pathway leading to 4-H-furo[3,2-f]pyrrolo[1,2-a][1,4]diazepines is described in five steps starting from 2-hydroxyketones via 2-amino-3-furonitriles.