A study of some pyridopyrazines and pyridopyrimidines

The d- and l-forms of 2H-octahydropyrido[1,2-a]pyrazine (I) have been prepared and their absolute configurations established. These configurations were confirmed by an optical rotary dispersion study. The infrared spectra of 2H-octahydropyrido[1,2-a]pyrazine (I), lH-octahydropyrido[ 1,2-a]pyrimidine (11) and 2H-octahydropyrido[ 1,2-c]pyrimidine (111) were compared with the infrared spectrum of quinolizidine. All of these spectra showed the Bohlmann bands characteristic of a trans ring structure. A few derivatives of these ring systems have been prepared.     

Regiospecific synthesis of 3-substituted imidazo[1,2-a]pyridines,imidazo[1,2-a]pyrimidines,and imidazo[1,2-c]pyrimidine

3-Substituted imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and imidazo[1,2-c]pyrimidine were obtained regiospecifically in yields of 35-92% in one pot by reaction of 2-aminopyridines or 2-(or 4-)aminopyrimidines, respectively, with 1,2-bis(benzotriazolyl)-1,2-(dialkylamino)ethanes.     

α,α-二乙酰基二硫缩烯酮和芳醛的缩合反应研究

在碱性条件下,α,α-二乙酰基二硫缩烯酮和芳醛的缩合反应受烷硫基的影响.α,α-二乙酰基二苄硫缩烯酮1和芳醛3缩合生成单面缩合脱乙酰基产物α-肉桂酰基二苄硫缩烯酮4;α,α-二乙酰基环二硫缩烯酮2和芳醛3缩合生成双面缩合产物α,α-二肉桂酰基环二硫缩烯酮5.     

吡啶并嘧啶类化合物的合成研究进展

综述了近二十年来吡啶并嘧啶类化合物的合成研究进展，介绍了三大类吡啶并嘧啶类化合物的主要结构类型：吡啶并[2,3-d]嘧啶类化合物、吡啶并[1,2-a]嘧啶类化合物、吡啶并[4,3-d]嘧啶类化合物的相关合成方法及新进展。     

Reactions of some new thienothiophene derivatives

Facile and convenient syntheses of bisdimethylthieno[2,3-b]thiophen-2,5-diyl bis(oxazole-2-amine), bis(1H-imidazol-2-amine), bis((3a)-H-indole),[1,2-a]pyrimidine), bis(1H-imidazo[1,2-b][1,2,4]triazole) and bis(9H-benzo[d]imidazo[1,2-a]imidazole) derivatives incorporating a thieno[2,3-b]thiophene moiety from the versatile and readily accessible 1,1'(3,4-dimethylthieno[2,3-b]thiophene-2,5-diyl)-bis(2-bromo-ethanone) (1) are described.     

α,α-二乙酰基二苄硫缩烯酮的碱催化脱乙酰基反应及缩合反应机理研究

α-羰基二硫缩烯酮是一类极其重要的有机合成中间体，烷硫基对该类具有推-拉电子效应的共轭体系的性质影响很大。据此，我们率先提出了烷硫基对α-羰基二硫缩烯酮类化合物的化学行为具有调控作用的观点，并将其归因于空间电子因素的作用，α-乙酰基-α′-羰基二苄硫缩烯酮(1)具有多反应性特征。近来，我们利用该特征在氢氧化钠催化下通过化合物1的环合合成了多取代噻吩类化合物；在乙醇钠-醋酸铅作用下经乙氧基对化合物1的苄硫基的取代实现了α-羰基-O，O-缩烯酮的合成。     

Chemistry of acyl(imidoyl)ketenes. 8*. Thermolysis of 3-alkoxycarbonyl- 5-phenyl-1,2,4,5-tetrahydropyrrolo[1,2-a]- quinoxaline-1,2,4-triones. Structure of 2-(3-oxo-4-phenyl-3,4-dihydro-2-quinoxalinyl)- 2,4-di(ethoxycarbonyl)-6-phenyl-2,3,5,6-tetrahydro- 1h-pyrido[1,2-a]quinoxaline-1,3,5-trione

3-Alkoxycarbonylmethylene-1-phenyl-1,2,3,4-tetrahydro-2-quinoxalones, obtained by the interaction of dialkyl esters of oxaloacetic acid and N-phenyl-o-phenylenediamine, react with oxalyl chloride with the formation of 3-alkoxycarbonyl-5-phenyl-1,2,4,5-tetrahydropyrrolo[1,2-a]quinoxaline-1,2,4-triones. Alkoxycarbonyl(2-oxo-1-phenyl-1,2-dihydro-3-quinoxalinyl)ketenes, generated on thermal decarbonylation of the latter, are stabilized by participation in a [4+2] cyclodimerization reaction with the formation of 2,4-di(alkoxycarbonyl)-2-(3-oxo-4-phenyl-3,4-dihydro-2-quinoxalinyl)-6-phenyl-2,3,5,6-tetrahydro-1H-pyrido[1,2-a]quinoxaline-1,3,5-triones. The crystal and molecular structure of the di(ethoxycarbonyl) derivative have been investigated by X-ray structural analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1501–1506, October, 2004.     

Palladium-catalyzed regioselective arylation of imidazo[1,2-a]pyrimidine

Imidazo[1,2-a]pyrimidine can be arylated at the 3-position with aryl bromides in the presence of base and a catalytic amount of palladium. This provides an efficient one-step synthesis of 3-arylimidazo[1,2-a]pyrimidines from the unsubstituted heterocycle. [reaction: see text]     

Utility of a Pyrimidin-2-Thione Derivative in Synthesis of New Fused Thiazolo[3,2-a]pyrimidines

A pyrimidin-2-thione derivative 2 was prepared and treated with 1,2-dibromoethane, chloroacetic acid and ethyl chloroacetate to give the alkylation products 3,4,9,5, respectively. Furthermore, the reaction of 2 with acrylonitrile and hydrazine hydrate yielded the pyrimidino[2,1-b]thiazine derivative 7, and [1,2,4]-triazolo[4,3-a]pyrimidine 8. Compound 9 was used as the key starting material for synthesis of thiazolo[3,2-a]pyrimidine and pyrano[2′,3′ :4,5]thiazolo[3,2-a]pyrimidine derivatives 10–13, through the reaction with ethyl acetate, malononitrile, hydrazine hydrate, β-aroylacrylic acid, and chalcone, respectively. Treatment of compound 5 with 3,5-dibromo-2-aminobenzoic acid in refluxing butanol gave the 3,1-benzoxazinone derivative 6. The structure assignment of the new compounds is based on chemical and spectroscopic evidence.     

Intermolecular 1,5-dipolar cycloaddition reaction of tungsten-containing vinylazomethine ylides leading to seven-membered heterocycles

[STRUCTURE: SEE TEXT] Intermolecular 1,5-dipolar cycloaddition reaction of tungsten-containing vinylazomethine ylide, generated from o-(alk-3-en-1-ynyl)phenylbenzaldimines and tungsten carbonyl complex, with ketene acetals proceeds efficiently to give azepino[1,2-a]indole derivatives in good yield. Formation of [5+2] or [3+2] cycloadducts can be controlled by an appropriate choice of dipolarophile.     

Chloral as a formylating agent for some bridge heterosystems

The interaction of condensed nitrogen-containing bridge systems with chloral has been studied and the high sensitivity of the reaction to the -excess of the initial heteroaromatic system has been established. It has been shown that chloral is a convenient formylating agent for systems with a moderate -excess —imidazo[l,2-a]imidazole, 9H-imidazo[1,2-a]benzimidazole, imidazo[1,2-a]pyridine, imidazo[1,2-a]naphtho[2,3-d]imidazole. Heterocycles with a high -excess (indolizine, pyrrolo[1,2-a]benzimidazole) form cyanine dyes under the action of chloral. Systems with a lowered -excess (1H-imidazo[1,2-a]benzimidazole, imidazo[1,2-a]quinoline, imidazo[2,1-a]isoquinoline, imidazo[1,2-a]perimidine, imidazo[5,1-b]benzoxazole, imidazo[1,2-a]benzothiazole, and imidazo[1,2-a]pyrimidine) do not react with chloral in a neutral medium. However, in a number of cases their foraylation can be carried out in an acid medium.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 528–537, April, 1980.     

Isocyanate acting as a carbonyl precursor: pyridyl group-assisted formation of 4H-pyrido[1,2-a]pyrimidin-4-ones from ketimines and isocyanates

By the reactions of ketimines bearing a pyridyl or a picolyl group on a nitrogen atom of the imine moiety with tosylisocyanate, 4H-pyrido[1,2-a]pyrimidin-4-one derivatives could be obtained in quantitative yields. In these reactions, tosylisocyanate acts as a carbonyl precursor. The pyridyl or picolyl group is a key functional group because it is not only the constituent structure of the 4H-pyrido[1,2-a]pyrimidin-4-one framework but also the promoter of the formation of a ketene intermediate.     

Formal fusion of a pyrrole ring onto 2-pyridyl and 2-pyrimidyl cations: one-step gas-phase synthesis of indolizine and its derivatives

Two ortho-hetarynium ions, the 2-pyridyl and 2-pyrimidyl cations, react promptly with 1,3-dienes in the gas phase by annulation, formally by fusion, onto the ions of a pyrrole ring. This novel reaction proceeds through an initial polar [4 + 2+] cycloaddition across the C[triple bond]N+ bond, followed by fast ring opening, a [1,4-H] shift, and finally a recyclization that results in a contraction of a six- to a five-membered ring and dissociation by the loss of a methyl radical. For the 2-pyridyl cation, this reaction yields ionized indolizines (pyrrolo[1,2-a]pyridines), while for the 2-pyrimidyl cation, it gives ionized pyrrolo[1,2-a]pyrimidines. The annulation reaction, performed in the rf-only collision quadrupole of a pentaquadrupole (QqQqQ) mass spectrometer, occurs readily with both 1,3-butadiene and isoprene, and is thermodynamically and kinetically favored as predicted by ab initio calculations. Ortho-hetarynium ions and 1,3-dienes provide, therefore, the two building blocks for the efficient one-step gas-phase synthesis of ionized bicyclic pyrrolo[1,2-a]pyridine (indolizine) and pyrrolo[1,2-a]pyrimidine, as well as their analogues and derivatives.     

Novel route for the transformation of a pyrimidine ring using hydrazides

It has been shown from X-ray structural analytical data that the reaction of 2-ethoxycarbonylmethyl-1,4,6-trimethylpyrimidinium iodide with carboxylic acid hydrazides gives pyrazolo[1,5-a]pyrimidine derivatives and not the isomeric triazolo[4,3-a]pyridines previously reported. This novel and previously unreported rearrangement of 1,2-dialkylpyrimidinium salts occurs via recyclization of the pyrimidine ring with inclusion of a fragment of the nucleophilic reagent into the transformation product. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 262–275, February, 2006.     

A cascade reaction of azolopyrimidines. Synthesis of unusual indole and azaindole derivatives

The reaction of bromo substituted pyrido[3',2':4,5]pyrrolo-[1,2-c]pyrimidine and pyrimido[1,6-a]indole methyl carboxylates with primary amines is described. The expected amide formation occurs but it is followed by an unexpected cascade process involving attack of the amine to the pyrimidine ring, opening of the pyrimidine ring, loss of the bromine substituent and competitive cyclizations to afford unusual imidazolidene substituted indoles and azaindoles.     

Pyrimidine acyclo-C-nucleosides by ring transformations of 2-formyl-L-arabinal

The protected 2-formyl-L-arabinal 2 reacted with thiourea and cyanamide in the presence of sodium hydride to afford via ring transformations the 5-[1R,2S-1,2- bis(benzyloxy)-3-hydroxypropyl]-1,2-dihydropyrimidines 3 and 4, respectively. Similarly, treatment of 2 with 3-amino-2H-1,2,4-triazole yielded 6-[1R,2S-1,2- bis(benzyloxy)-3-hydroxypropyl][1,2,4]-triazolo[1,5-a]pyrimidine (5).     

Heterocyclizations with tosylmethyl isocyanide derivatives. A new approach to substituted azolopyrimidines

An efficient synthesis of substituted azolopyrimidines such as pyrido[3',2':4,5]pyrrolo[1,2-c]pyrimidines, pyrimido[1,6-a]indoles, benzo[4,5]imidazo-[1,2-c]pyrimidines, an imidazo[1,2-c]pyrimidine, and pyrazolo[1,5-c]pyrimidines is described. The method involves the reaction of N-protected bromomethylazoles and tosylmethyl isocyanide (TosMIC) derivatives in nonanhydrous media. The study of the reaction conditions shows that the method is only successful under phase-transfer conditions (CH2Cl2/30% aq NaOH) using benzyltriethylammonium chloride as a catalyst.     

Multiple coordination geometries supported by methylene-linked guanidines

The methylene-linked bicyclic guanidine based on the 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) framework provides a versatile platform able to support trigonal-planar, tetrahedral, and square-planar metal centers.     

Synthesis and anti-inflammatory activity of imidazo [1,2-a] pyrimidine derivatives

A series of imidazo[1,2-a]pyrimidine derivatives substituted adjacently with two aryls at positions 2 and 3 were designed and synthesized in order to improve their anti-inflammatory activities. Biological tests suggested that these compounds have antiinflammatory activities with COX-2 selectivity to some extent.     

A simple and efficient one-pot novel synthesis of pyrazolo[3,4-b][1,8]naphthyridine and pyrazolo[3,4-d]pyrimido[1,2-a]pyrimidine derivatives as anti-inflammatory agents

Research on Chemical Intermediates - An efficient one-pot synthesis of novel pyrazolo[3,4-b][1,8]naphthyridine and pyrazolo[3,4-d]pyrimido[1,2-a]pyrimidine derivatives has been investigated from...