Novel syntheses of murrayaquinone A and furostifoline through 4-oxygenated carbazoles by allene-mediated electrocyclic reactions starting from 2-chloroindole-3-carbaldehyde.

The formal total synthesis of murrayaquinone A (1) and the total synthesis of furostifoline (5) were completed by the construction of 4-oxygenated 3-methylcarbazoles 7 based on a new type of electrocyclic reaction through 2-alkenyl-3-allenylindole intermediates 8 derived from the 2-alkenyl-3-propargylindoles 9, starting from 2-chloroindole-3-carbaldehyde (11). The N,O-bisbenzyloxymethyl group of 16c and 22 underwent a Birch reduction followed by treatment with Triton B to produce the known 4-hydroxy-3-methylcarbazole (7a) and 4-hydroxy-3-methylfuro[3,2-a]carbazole (7b) as precursors of murrayaquinone A (1) and furostifoline (5), respectively. The trifluoromethanesulfonyloxy-3-methylfuro[3,2-alcarbazole (24), prepared from 7b, was subjected to reductive cleavage to provide furostifoline (5).     

An efficient one-pot synthesis of thiophene-fused pyrido[3,2-a]azulenes via Gewald reaction

A simple and efficient procedure was developed for the synthesis of 11H(2H)-4-oxothiophene[3',4':6,5]pyrido[3,2-a]azulene-10-carboxylates(3) in moderate to good yields via the Gewald reaction of ethyl 1-cyanoacetyl-2-methoxyazulene-3-carboxylate(1) with carbonyl compounds(2) and elemental sulfur utilizing imidazole as catalyst.This reaction provides a new procedure for synthesis of pyridinone-fused azulenes.     

An Efficient Synthesis of Ethyl 7-Chloro-6-fluoro-1-methyl-4-oxo-1,4-dihydro-[1, 3]thiazeto[3, 2-a]quinoline-3-carboxylate as Intermediate of the Prulifloxacin Containing Tricyclic Fluoroquinolone

The fluoroquinolones such as ciprofloxacin and sparfloxacin have been widely used for the treatment of various bacterial infections1. Their mechanism of action is believed to be associated with inhibition of bacterial DNA gyrase2. Moreover, recent studies…     

An Efficient Synthesis of Ethyl 7-Chloro-6-fluoro-l-methyl-4-oxo-1, 4-dihydro-[1, 3]thiazeto[3, 2-a]quinoline-3-carboxylate as Intermediate of the Prulifloxacin Containing Tricyclic Fluoroquinolone

Novel ethyl 7-chloro-6-fluoro-l-methyl-4-oxo-1, 4-dihydro-[1, 3]thiazeto[3, 2-a]quino- line-3-carboxylate 2 was prepared from 3-chloro-4-fluoroaniline in eight steps. It can be used as a new intermediate for the synthesis of tricyclic fluoroquinolones.     

Synthesis of Dispiro[indoline-3,3′-pyrrolo[2,1-a]isoquinoline-1′,2′′-thiazolo[3,2-a]pyrimidine] Derivatives via Cycloaddition Reactions

Russian Journal of General Chemistry - The 1,3-dipolar cycloaddition reaction of ethyl (Z)-2-(2-methoxy-2-oxoethylidene)-7-methyl-3-oxo-5-aryl-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate...     

Nitrenes-XV: 1-Hydroxymethyl-4,5-dimethoxy-7H-azirino[1,2-a]-indole-7a-carboxylic acid γ-lactone,a nitrene addition compound

Triethyl phosphite deoxygenation of α-(6-nitroveratrylidene)-γ-butyrolactone 1 under moderate conditions affords a mixture of 3-(6-nitroveratryl)-2(5H)-furanone 5, α-(6-ethylaminoveratrylidene)-γ-butyrolactone 6 and 1-hydroxymethyl-4,5-dimethoxy-7H-azirino[1,2-a]indole-7a-carboxylic acid γ-lactone 7, in addition to 3,4-dihydro-7,8-dimethoxy[1,3-a]oxazino[3,4-a]indol-1-one 2, ethyl 5,6-dimethoxyindole-2-carboxylate 3, and 2,3-dihydro-6,7-dimethoxyfuro[2,3-b]quinoline 4, obtained under more drastic reaction conditions.The isolation of lactones 5 and 7 provides strong evidence for the intermediacy of nitrenes in this reaction which appears to provide the first example of intramolecular aziridine formation from a nitro-aromatic compound and triethyl phosphite.     

An efficient ultrasonic-assisted synthesis of ethyl-5-(aryl)-2-(2-alkokxy-2-oxoethylidene)-7-methyl-3-oxo-3, 5-dihydro-2H-thiazolo [3, 2-a] pyrimidine-6-carboxylate derivatives

Dihydropyrimidinone derivatives were prepared by tri-component reaction of ethyl aceto acetate, aldehydes and thiourea in the presence of modified montmorillonite nanostructure as a catalyst and used as key intermediates for the synthesis of ethyl-5-(aryl)-2-(2-alkokxy-2-oxoethylidene)-7-methyl-3-oxo-3,5-dihydro-2H-thiazolo[3,2-a]pyri midine-6-carboxylate derivatives with use of diethyl and dimethyl acetylene dicarboxylate by two methods: (a) in methanol as a solvent under ultrasonic irradiation at ambient temperature (b) in methanol as a solvent at ambient temperature (conventional magnetic stirring). Ultrasound-assisted synthesis provides excellent yields in short reaction times (15–25 min) at room temperature.     

Synthesis of 3-Substituted Pyrido[4′,3′:4,5]thieno[2,3-d]pyrimidines and Related Fused Thiazolo Derivatives

New ethyl 3-(substituted)-4-oxo-2-thioxo-1,2,3,4,5,6,7,8-octahydropyrido[4',3':4,5]thieno-[2,3-d]pyrimidine-7-carboxylates ( 3a , b ), ( 6 ),( 11-13 ), ethyl 3-methyl-5-oxo-2,3,6,9-tetrahydro 5 H -pyrido[4',3':4,5]thieno[2,3-d][1,3]thiazolo[3,2-a]pyrimidine-8(7H)-carboxylate ( 4 ), and ethyl 2-methyl-5-oxo-2,3,6,9-tetrahydro-5 H -pyrido[4',3':4,5]thieno[2,3-d][1,3]thiazolo[3,2-a]-pyrimidine-8(7H)-carboxylate ( 8 ) have been synthesized from diethyl 2-isothiocyanato-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3,6-dicarboxylate 1. The structure of these compounds as well as their intermediates have been established by their spectral data.     

A novel heterocyclic compound. Synthesis and reactivities of an oxazolo[3,2-a]thieno[3,2-d]-pyrimidine derivative

A practical preparation of 2,3-dihydro-5H-oxazolo[3,2-a]thieno[3,2-d]pyrimidin-5-one (2) from methyl 3-aminothiophene-2-carboxylate in two steps was developed. The addition reactions of various nucleophiles to 2 were investigated and oxazole-ring-opened compounds were produced (5, 6, 12, 13 and 14). Desulfurization reaction of 2 with Raney Ni gave an oxazolo[3,2-a]pyrimidine derivative (15). It was found that 2 showed potent anti-gastric secretion activity.     

Synthesis of novel isoxazolyl bis-thiazolo[3,2-a]pyrimidines

A new synthetic strategy for the synthesis of novel 3-(3-(3-methyl-4-nitroisoxazol-5-yl)-2-phenyl-1-(5,7-diaryl-7H-thiazolo[3,2-a]pyrimidin-3-yl)propyl)-5,7-diaryl-7H-thiazolo[3,2-a] pyrimidines(7a-i) analogues is described.Reaction of 3-(2(3-methyl-4-nitroisoxazole-5-yl)-1-phenylethyl)pentane-2,4-dione(3) with two moles of thiourea in presence of iodine and CuO afforded 4-(1-(2-aminothiazol-4-yl)-3-(3-methyl-4-nitroisoxazol-5-yl)-2-aryl propyl-thiazol-2-amine(5).Compound 5 on reaction with two moles of chalcone(6) furnished novel 3-(3-(3-methyl-4-nitroisoxazol-5-yl)-2-phenyl-1-(5,7-diaryl-7H-thiazolo[3,2a]pyrimidin-3-yl)propyl)-5,7-diaryl-7H-thiazolo[3,2-a] pyrimidines(7a-i).     

新型Bluco类β-内酰胺酶分子探针的合成

以2-氰基-6-羟基苯并噻唑为原料,与溴乙醛缩二乙醇缩合制得缩醛后再水解合成中间体6-(2-羰乙基)苯并[d]噻唑-2-甲腈(2);7-苯乙酰氨基-3-氯甲基头孢菌烷酸二苯甲酯依次经碘代和Wittig反应得(Z)-3-[3-(2-氰基苯并[d]噻唑-6-氧)丙-1-烯]-8-羰基-7-(2-苯乙酰氨基)-5-噻-1-氮[4.2.0]辛-2-烯-2-甲酸二苯甲酯(5);5经脱保护、缩合和氧化反应合成了3个新的Bluco类似物,其结构经1H NMR,13C NMR和HR-MS(ESI)表征。     

Synthesis and antibacterial activity of novel 7-substituted-6-fluoro-1- fluoromethyl-4-oxo-4H-[1,3thiazeto[3,2-a]quinoline-3-carboxylic acid derivatives

A series of 7-substituted-6-fluoro-1-fluoromethyl-4-oxo-4H- [1,3]thiazeto[3,2-a]quinoline-3-carboxylic acid derivatives (2a-1) was prepared and evaluated for antibacterial activity. These compounds were obtained by deacylation of 4-benzoyloxy-2-(1-chloro-2-fluoroethyl)thio-6,7- difluoroquinoline-3-carboxylate (10) and subsequent intramolecular cyclization followed by substitution with cyclic amines and then hydrolysis. The intramolecular cyclization reaction of 18, one of the diastereomers (17, 18) revealed that the cyclization reaction proceeded through an inversion to afford (-)-11a in good chemical and optical yield. The enantiomers of 2a were prepared from the enantiomers of 11a, which were obtained by the optical resolution of the racemate using high-performance liquid chromatography (HPLC). Compounds 2a,b showed excellent in vitro and in vivo antibacterial activity against both gram-negative and gram-positive bacteria including quinolone and Methicillin-resistant Staphylococcus aureus.     

Research on imidazo[1,2-a]benzimidazole derivatives.

3-Alkoxycarbonyl-2-arylimidazo[1,2-a]benzimidazoles were synthesized by alkaline cleavage of 3-trichloromethyl ketones of the imidazo[1,2-a]benzimidazole series, which are formed by acylation of this three-ring system with trichloroacetyl chloride. The same compounds were also obtained by esterification of the corresponding 3-carboxylic acid. The haloform reaction with 3-acetyl-2-phenylimidazo[1,2-a]benzimidazole proceeds anomalously and leads to bis(9-methy1-2-phenylimidazo[1,2-a]benzimidazo1-3-yl)-2-buten-1,4-dione, the structure of which was confirmed by independent synthesis.See [1] for communication XV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 522–525, April, 1978.     

Complexes of functionalized dipyrido[3,2-a:2',3'-c]-phenazine: a synthetic, spectroscopic, structural, and density functional theory study

The ligands 11-bromodipyrido[3,2-a:2',3'-c]phenazine and ethyl dipyrido[3,2-a:2',3'-c]phenazine-11-carboxylate have been prepared and coordinated to ruthenium(II), rhenium(I), and copper(I) metal centers. The electronic effects of substitution of dipyrido[2,3-a:3',2'-c]phenazine (dppz) have been investigated by spectroscopy and electrochemistry, and some photophysical properties have been studied. The crystal structures of [Re(L)(CO)(3)Cl] (L = ethyl dipyrido[3,2-a:2',3'-c]phenazine-11-carboxylate or 11-bromodipyrido[3,2-a:2',3'-c]phenazine) are presented. Density functional theory calculations on the complexes show only small deviations in bond lengths and angles (most bonds within 0.02 Angstroms, most angles within 2 degrees) from the crystallographic data. Furthermore, the vibrational spectra of the strongest Raman and IR bands are predicted to within an average 6 cm(-1) for the complexes [Re(L)(CO)(3)Cl] and [Cu(L)(triphenylphosphine)(2)]BF(4) (in the 1000-1700 cm(-1) region). Spectroscopic and electrochemical evidence suggest that reduction of the complex causes structural changes across the entire dppz ligand. This is unusual as dppz-based ligands typically have electrochemical properties that suggest charge localization with reduction on the phenazine portion of the ligand. The excited-state lifetimes of the complexes have been measured, and they range from ca. 200 ns for the [Ru(L)(2,2'-bipyridine)(2)](PF(6))(2) complexes to over 2 mus for [Cu(11-bromodipyrido[3,2-a:2',3'-c]phenazine)(PPh(3))(2)](BF(4)) at room temperature. The emission spectra suggest that the unusually long-lived excited states of the copper complexes result from metal-to-ligand charge transfer (MLCT) transitions as they are completely quenched in methanol. Electroluminescent films may be fabricated from these compounds; they show MLCT state emission even at low doping levels [<0.1% by weight in poly(vinylcarbazole) polymer matrix].     

An efficient synthesis of novel pyridothieno-fused thiazolo[3,2-a]pyrimidinones via Pictet–Spengler reaction

An efficient method for the synthesis of novel pyrido[3',2':4',5']thieno[3',2':2,3]pyrido [4,5:d][1,3]thiazolo[3,2-a]pyrimidine-4-one derivatives (5) has been developed using a Pictet-Spengler reaction between 2-(3-aminothieno[2,3-b]pyridin-2-yl)thiazolo[3,2-a] pyrimidin-5-one (3), which could be obtained from the condensation of 7-(chloromethyl)-5H-thiazolo[3,2-a]pyrimidin-5-one (1) with 3-cyanopyridine-2-thione (2) via Thorpe-Ziegler isomerization, and aromatic aldehydes under NH₂SO₃H as catalysis in good yields.     

4-(Het)aryl-4,7-dihydroazolopyrimidines and Their Tuberculostatic Activity

Russian Journal of Organic Chemistry - Structural analogs of a promising antituberculous agent, ethyl 5-methyl-7-(thiophen-2-yl)-4,7-dihydro[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate have been...     

Synthesis, structure and properties of N-acetylated derivatives of methyl 5-amino-1H-[1,2,4]triazole-3-carboxylate

Methyl 5-amino-1H-[1,2,4]triazole-3-carboxylate hydrochloride (1). and free ester (2). were obtained and 2 was reacted with Ac(2)O to give the acetylated products 3-6. Compounds 1-6 were studied using HPLC, GC-MS, FTIR and multinuclear NMR spectroscopy, including the cross-polarisation magic angle spinning (CPMAS) technique. The results of the acetylation of 2 were compared to those of the acetylation of 5-amino-1H-[1,2,4]triazole, and for 2 a significant decrease in the susceptibility to acetylation was found. The reaction of 2 with Ac(2)O at 20 degrees C, regardless of the amount and the concentration of the latter, including neat Ac(2)O, proceeds fully regioselectively and leads to one product: methyl 1-acetyl-5-amino-1H-[1,2,4]triazole-3-carboxylate (3). In sharp contrast to 5-amino-1H-[1,2,4]triazole, neither an additional monoacetylated isomer, whether annular or exocyclic, nor any diacetylated derivative could be detected. The diacetylation of 2 requires the process to be carried out in neat boiling Ac(2)O and, as in the case of 5-amino-1H-[1,2,4]triazole, gives two diacetylated isomers. These are methyl 1-acetyl-3-(acetylamino)-1H-[1,2,4]triazole-5-carboxylate (4) and 1-acetyl-5-(acetylamino)-1H-[1,2,4]triazole-3-carboxylate (5). Hypothetical pathways of their formation have been suggested. A mixture of 4 and 5 upon hydrolysis of the ring acetyl group gives the monoacetylated derivative methyl 5-(acetylamino)-1H-[1,2,4]triazole-3-carboxylate (6). The spectroscopic, structural and conformational characteristics of compounds 1-6 have been given and methods for their preparation have been provided.     

Au(i)-catalyzed and iodine-mediated cyclization of enynylpyrazoles to provide pyrazolo[1,5-a]pyridines

Pyrazolo[1,5-a]pyridines and 6-iodopyrazolo[1,5-a]pyridines were synthesized by gold-catalyzed and iodine-mediated cyclization of enynylpyrazoles in good to excellent yields, respectively. The iodinated adducts were further converted to 6-arylpyrazolo[1,5-a]pyridines via Suzuki-Miyaura coupling reaction and 6-cyanopyrazolo[1,5-a]pyridine by Ullmann condensation reaction. One of the cyclization adducts, 2-(4-fluorophenyl)pyrazolo[1,5-a]pyridine, was converted to a p38 kinase inhibitor, 2-(4-fluorophenyl)-3-(4-pyridinyl)pyrazolo[1,5-a]pyridine, in two steps.     

On the synthesis of protopine alkaloids

For the synthesis of protopine alkaloids, we studied a reaction sequence based on a ring enlargement of indeno[2,1-a][3]benzazepines by a singlet oxygen oxygenation, followed by conversion of an amide carbonyl group of the resultant 10-membered keto-lactam to a methylene group, which is the last step for completion of the synthesis. The key substances, indeno[2,1-a][3]benzazepines, were prepared by Bischler-Napieralski cyclization of alkoxy-substituted 1-(2-bromobenzyl)-3-benzazepin-2-ones. Steric effects of the substituents in this synthesis were examined.     

Synthesis of pyrrolo[1,2-a]indoles: vilsmeier formylation of some 3-methylindol-2-yl ketones and 3(3-methylindol-2-yl)propenoic ester

3-Methylindol-2-yl methyl ketone reacted with phosphoryl chloride in dimethylformamide to give 3-chloro-3(3-methylindol-2-yl), propenal (4). 2-Carbomethoxy- and 2-carbethoxy-1-chloro- 9H-pyrrolo[1,2-a]indol-9-ylidene acetaldehyde (10a and b) were formed by reaction with the same reagent of 3(3-methylindol-2-yl) propenoate (7) and 3(3-methylindol-2-yl)-3-oxopropanoate (2) respectively. In the latter case, 2-carbethoxy-1-chloro-3-dimethylamino-9-methyl-3H-pyrrolo[1,2-a]indole (9b) was isolated as an intermediate. The structure of the pyrroloindolylidene acetaldehydes was proved by synthesis of the chromophore from 4-acetyl-3-methyl-1-phenyl-pyrrole-2-carboxylate (26). The preparation and behaviour of 1-phenylpyrrole-2,4- and 3,4-dicarboxylates, monomethylated in the pyrrole ring, is described. These compounds were prepared during a search for a satisfactory route to a starting material for the synthesis of compounds related to 10a and b. The saponification of such diesters is remarkably selective, and in the case of the 2,4-dicarboxylates, contradicts accepted generalisations concerning the lability of pyrrole α,β-diesters to selective hydrolysis.