Synthesis of some 7-substituted thiazolino [3,2-a] benzimidazoles

The 7-amino (IV) and 7-acetamido (I) derivatives of thiazolino[3,2-a]benzimidazole were synthesized. The IR spectra of I, its deutero derivative, and a number of intermediates were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 177–179, February, 1972.     

Structure and reactions of a thiazolino[3,2-a]pyrimidine carbinolamine

Ethyl 4-chloroacetoacetate condenses with 4-amino-6-hydroxy-2-pyrimidinethiol to yield ethyl 3-hydroxy-5-oxo-7-aminothiazolino[3,2-a]pyrimidin-3-acetate ( 3 ), and not ethyl 3-hydroxy-5-amino-7-oxothiazolino[3,2-a]-pyrimidin-3-acetate, as previously reported. This compound reacts with ammonia to produce ethyl 4-(6′-amino-4′-oxo-2′-pyrimidinethiol)-3-aminocrotonate ( 8 ), the open chain structure of which accounts for the cyclization of 3 to the poly-cyclic lactam, 6a-hydroxy-5,6,6a,7-tetrahydro-8-thia-1,4-diazacycl[3.3.2]azine-2,5-dione, rather than the sterically more favorable lactone, when 3 was treated with triethylamine. Some other reactions of 3 are described, and the structures of 3 and 8 were comfirmed by single crystal X-ray diffraction analysis.     

Synthesis of pyridazino[1,6-a]benzimidazoles

The synthesis of eight pyridazino[1,6-a]benzimidazoles by a novel synthetic route is described. This relatively unexplored heterocyclic ring system is readily accessible starting from benzoylpropionic acids and phenylhydrazines in five steps. The interactions of these compounds with the benzodiazepine receptor are briefly mentioned.     

Synthesis of 4-alkylpyrazolo[1,5-a]benzimidazoles

2,4-Disubstituted pyrazole[1,5-a]benzimidazoles were obtained by the action of carboxylic acid anhydrides on 1-amino-2-methyl-3-alkylbenzimidazolium salts in the presence of potassium carbonate. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 814–817, June, 1980.     

Synthesis of indazolo[3,2-a]isoquinoline

Treatment of 1-(2′-nitrophenyl)isoquinoline with hot triethylphosphite afforded indazolo[3,2-a]isoquino-line.     

Investigations of imidazo[1,2-a]benzimidazoles 26. 2-Halomethylimidazo[1,2-a]benzimidazoles and their reactive properties

Treatment of 2-aminobenzimidazoles with 1,3-dichloroacetone or radical bromination of 3-alkoxycarbonyl- or 3-acetyl-2-methylimisazo[1,2-a]benzimidazoles leads to the 2-halomethyl derivatives of this heterocycle. The lability of the halogen atom in the synthesized compounds has been demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 369–376, March, 1994.     

Synthesis of 3-dimethylphenylsilyl-substituted pyrido[1,2-a]benzimidazoles

Reductive cyclization of 1-(2,4-dinitrophenyl)-3-methyl-4-dimetkylphenyisililpyridinium chloride by the action of phenylkydrazine or hydrogen in the presence of Pd/C gave, for the first time, 7-nitro (amino)-3 dimethylphenylsilylpyrido[l, 2-affienzimidazoles.Russian University of the Friendship of Nations, Moscow, 117923. Translated from Khimiya Geterots ikl icheskikh Soedinenii, No, 3, pp. 338–341, March, 1996. Original article submitted November 27, 1995.     

苯并噁唑[3,2-a]吡啶盐两性离子化合物的合成

常温下,在丙酮与水的混合介质中(V:V=1:1),4-羟基香豆素类化合物与1,4-苯醌、2-甲氧基吡啶反应,生成5个未见文献报道的苯并噁唑两性离子化合物.产物经MS,1HNMR,元素分析表征,确定了其化学结构.     

Synthesis and deamination of 9-aminoimadazo[1,2-a]benzimidazoles

The reaction between 1,2-diaminobenzimidazole and -halocarbonyl compounds has given some novel 9-aminoimidazo [1,2-a]benzimidazoles. On treatment with nitrous acid or potassium hydroxide in DMSO, these compounds give, in addition to the deaminated compounds, 3-nitroso-derivatives of the deamination products. In the system DMSO-KOH, 9-benzylideneaminoimidazobenzimidazoles are converted smoothly into 1(9H)-imidazobenzimidazoles. It is shown that 3-nitroso-derivatives which are unsubstituted in the NH group exist predominantly in the hydroxyimino form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1517–1523, November, 1990.     

新型噻唑并[3,2-a]嘧啶类化合物的合成

5-乙氧羰基-4-芳基-6-甲基-3,4-二氢嘧啶-2-酮与丁炔二酸二甲酯反应, 合成了系列新的噻唑并[3,2-a]嘧啶类化合物, 反应具有时间短、收率高、后处理简单等优点. 采用NMR (1H, 13C, COSY, HSQC和HMBC), IR等多种谱学技术, 结合元素分析对产物进行详细表征, 通过对目标产物的1,3-偶极环加成的衍生化产物进行X射线单晶衍射而确定目标产物的结构.     

Synthesis of novel dihydrothiazolo[3,2-a]pyrimidinone derivatives

Condensation of 2-amino-4-hydroxy-2-mercaptopyrimidine (2) hydrate and ethyl 4-bromocrotonate gave a mixture of ethyl 7-amino-2,3-dihydro-5-oxo-5H-thiazolo[3,2-a]pyrimidine-3-acetate (4) and 2a,3-dihydro-1-thia-5,8,8b-triazaacenaphthylene-4,7(2H)-dione (5) whereas reaction of 2 with 4-bromocrotononitrile afforded only 7-amino-2,3-dihydro-5-oxo-5H-thiazolo[3,2-a] pyrimidine-3-acetonitrile. Reaction of the tricycle 5 (which was isolated as a hemihydrate) with excess methyl iodide/potassium carbonate in dimethylformamide resulted in both ring hydrolysis and methylation to give 3,4-dihydro-1,7-dimethyl-4- [(methylthio)methyl]-2H-pyrimido[1,6-a]pyrimidine-2,6,8(1H,7H)-trione (10). Methylating 5 with excess methyl iodide/sodium methoxide in methanol also resulted in ring fragmentation and methylation but instead afforded methyl 7-methyl-amino-2,3-dihydro-5-oxo-7H-thiazolo[3,2-a]pyrimidine-3-acetate. The mechanistic aspects of these reactions are discussed.     

One-Pot Synthesis of Thiazolidino [3,2-a] Pyrimidine Derivatives

Reaction of 2-aminothiazoline with an aromatic aldehyde and an activated methylene group (malonitrile, diethylmalonate or ethylcyanoacetate) gave the title compounds. The structures are unambiguously assigned using spectroscopic data and chemical proofs.     

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).     

Oxazolo[3,2-a]pyridinium and oxazolo[3,2-a]pyrimidinium salts in organic synthesis

The methods for the synthesis of oxazolo[3,2-a]pyridinium and oxazolo[3,2-a]pyrimidinium salts and their reactivities are reviewed. Both systems exhibit ambident properties in reactions with nucleophiles; depending on the substituents and the reagents, both the oxazole and azine rings can undergo opening and transformations. A number of new methodologies involving oxazolopyridinium and oxazolopyrimidinium salts for the design of functionalized oxazoles, imidazoles, fused pyrroles, and other heterocyclic systems are generalized. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 831–848, April, 2008.