An investigation of the minimal structural conditions lor the dirnroth-type rearrangement in the polyazaindolizine series

In the imidazo[1,2]diazine series, only the imidazo[1,2-a]- and [1,2-c] pyrimidine systems were found to undergo a Dimroth-type rearrangement under basic aqueous conditions. The electronic and steric factors influencing the rearrangement rates of methyl substituted imidazo-[1,2-a] pyrimidines are discussed.     

Formylation of Furyl-substituted Imidazo[1,2-a]pyridine, Imidazo[1,2-a]pyrimidine and Imidazo[2,1-b]thiazole

Vilsmeier formylation of 2-(2-furyl)-substituted imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine, and also 6-(2-furyl)imidazo[2,1-b]thiazole with 1 mole of reagent occurs at the free position of the imidazole ring, while with an excess of the reagent it also occurs at the position 5 of the furyl group.     

Copper oxide nanoparticle catalysed synthesis of imidazo[1,2-a]pyrimidine derivatives,their optical properties and selective fluorescent sensor towards zinc ion

Synthesis of biologically active fused imidazo[1,2-a]pyrimidines were achieved via A³ coupling involving 2-aminobenzimidazole, aldehyde and terminal alkyne, followed by 6-endo-dig cyclization using copper oxide nanoparticles under solvent free condition. Further optical properties of imidazo[1,2-a]pyrimidines were studied which showed the effect of electron-donating and electron-withdrawing substitution on the fluorescence intensities of these compounds. Out of 20 compounds, 2,4-bis(4-methoxyphenyl)benzo[4,5]imidazo[1,2-a]pyrimidine can act as a fluorescent sensor for zinc ion with detection limit 4.74?μM, which is much lower than the maximum allowable zinc concentration in drinking water by WHO.     

Methyl 2-benzoylamino-3-dimethylaminopropenoate in the synthesis of heterocyclic systems. An attempt to prepare benzoylamino substituted azolo- and azinopyrimidines with a bridgehead nitrogen atom

Methyl 2-benzoylamino-3-dimethylaminopropenoate ( 2 ) was introduced as a new reagent for the preparation of fused pyrimidinones 4 from heterocyclic α-amino compounds in acetic acid. In this manner, derivatives of pyrido[1,2-a]pyrimidine 4a,b,f , pyrimido[1,2-b]pyridazine 4g , pyrimido[1,2-c]pyrimidine 4j , pyrazino[1,2-a]pyrimidine 4k , thiazolo[2,3-b]pyrimidine 41 , pyrazolo[1,5-a]pyrimidine 4m , and 1,2,4-triazolo-[1,5-a]pyrimidine 4n were prepared.     

Heterocyclization of 3-(R-amino)-3-methylthio-1-phenylpropenones and 5-benzoyl-6-methylthio-1,2-dihydropyridin-2-ones with 1,2- and 1,3-dinucleophilic reagents

The interaction of 3-(R-amino)-3-methylthio-1-phenylpropenones and 1-alkyl-5-benzoyl-3-ethoxy-carbonyl-6-methylthio-1,2-dihydropyridin-2-ones with N,N- and N,C-1,2- and 1,3-dinucleophiles proceeded regioselectively by [3 + 2] and [3 + 3] cyclocondensation with the formation of derivatives of pyrazole, benzimidazo[1,2-a]-pyridine, benzimidazo[1,2-a]pyrimidine, imidazo[1,2-a]pyrimidine, [1,2,4]triazolo[4,3-b]pyridazine, and 6,7-dihydro-2H-pyrazolo[3,4-b]pyridine. The regioselectivity of the reactions carried out was analyzed.     

Studies in the Imidazole Series. 100. Synthesis of Derivatives of Imidazo[1,2-a]pyrimidine from 2-Aminopyrimidines, Methyl Aryl Ketones, and Halogens

We have synthesized imidazo[1,2-a]pyrimidine derivatives by reaction of 2-aminopyrimidines with methyl aryl ketones and halogens (bromine, iodine). Using bromine leads to formation of 6-bromo- and 3,6-dibromo-substituted 2-arylimidazo[1,2-a]pyrimidines.     

Preparation of 2-aryl and 2-aryloxymethyl imidazo[1,2-a]pyridines and related compounds

A series of substituted 2-aryl imidazo[1,2-a]pyridines has been prepared in which a variety of substituents are introduced on the 4′-position of the phenyl ring and on the 3, 5 , 6 or 7 position of the heterocyclic ring. Most examples have acetamido, bromo, cyano, or formyl substituents at the 4′-position. Analogous imidazo-[2,1-b]fhiazoles and imidazo[1,2-a]pyrimidines have also been prepared. Another series of compounds consisting of 4′-formylphenoxymethyl derivatives of imidazole, the three positional isomers of pyridine, thiazole, benzimidazole and ring-substituted imidazo[1,2-a]pyridines has been prepared. 2-(4′-Formylphenylethenyl) derivatives of imidazole and imidazo[1,2-a]pyridine were also prepared.     

Fragmentations Principales de Mono-, Di-, Triet Tetra-azaindolizines Sous L'Impact Electronique

The principal fragmentations of 41 azaindolizines having an imidazo[1,2-a]pyridine, imidazo[1,5-a]pyrimidine, imidazo[1,5-b]-1,2,4-triazine, triazolo[2,3-b], -[4,3-b]-, -[3,4-c]- and -[3,2-c]-1,2,4-triazine structure are described. It is shown that each structure has its own characteristic fragmentation pathways except where a Dimroth rearrangement into an isomeric product can be postulated. The degradation scheme is correlated with the number and the position of the nitrogen atoms of the azaindolizines.     

Solid-phase synthesis of imidazo[1,2-a]pyridines and imidazo[1,2-a]pyrimidines

The synthesis of imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine derivatives by condensation between an α-bromoketone bound to solid support and various 2-aminopyridine or 2-aminopyrimidine derivatives was described. Either an acid labile linker or a base labile linker was used in this study.     

New derivatives of pyrimidine nucleosides: Synthesis,physico-chemical properties and biological activity

The paper reports the synthesis and physico-chemical data of eight new pyrimidine nucleosides C-4 substituted and two imidazo[1,2-c]pyrimidine nucleosides as well as preliminary results of their biological effects on neuroblastoma cells in culture.     

Heterocycles from Pyrazoloylhydroximoyl Chloride: Synthesis of Certain Quinoxaline,Benzothiadiazine, Benzoxadiazine,Quinazolinone, Imidazo[1,2-a]pyridine,Imidazo[1,2-a]pyrimidine,Isoxazole, Pyrazolo[3,4-d]pyridazine and Pyrrolidino[3,4-d]isoxazolin-4,6-dione Derivatives

3-Ethoxycarbonyl-5-methyl-1-(4-methylphenyl)-4-pyrazoloylhydroximoyl chloride (1) reacted with o-phenylenediamine, o-aminothiophenol, o-aminophenol and methyl anthranilate to afford 3-nitrosoquinoxaline, benzothiadiazine, benzoxadiazine, and 3-hydroxyquinazoline, respectively. Imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine and isoxazole derivatives were obtained via the reaction of 1 with 2-aminopyridine, 2-aminopyrimidine and the appropriate active methylene compounds, respectively. Pyrazolo[3,4-d]pyridazines, and pyrrolidino[3,4-d]isoxazolines derivatives were also synthesized. The structures of the newly synthesized compounds were established on the basis of spectral data and alternate synthesis whenever possible.     

Some novel heterocyclic systems derived from 7-amino-2,3-dihydro-8-nitro-1H-pyrrolo[1,2-α]benzimidazole and the corresponding diamine

The preparation of 7-amino-2,3-dihydro-8-nitro-1H-pyrrolo[1,2-a]benzimidazole from 1,4-diacetamido-2,3-dinitrobenzene is described. Reaction of this compound with 2,5-dimethoxytetrahydrofuran produces 2,3-dihydro-8-nitro-7-N-pyrrolo-1H-pyrrolo[1,2-a]benzimidazole, which can be cyclised to produce two new heterocyclic ring systems, 9,10-dihydro-8H-pyrrolo[1,2-a]pyrrolo(1′,2′:1,2]imidazo[5,4-f]quinoxaline and 9,10-dihydro-8H-pyrrolo[2,1-c]pyrrolo[1′,2′:1,2]imidazo[4,5-h][1,2,4]benzotriazine. The corresponding diamine, 7,8-diamino-2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole undergoes a variety of condensation reactions to produce several new heterocyclic systems, for example, with formic acid, 1,7,8,9-tetrahydroimidazo-[4,5-e]pyrrolo[2,1-6]benzimidazole is formed and with diacetyl, 9,10-dihydro-2,3-dimethyl-8H-pyrrolo-[1′,2′:1,2]imidazo[5,4-y]quinoxaline is obtained.     

Efficient synthesis and antioxidant activity of coelenterazine analogues

A convenient and highly convergent method for the synthesis of new imidazo[1,2-a]pyridine-based coelenterazine analogues is reported. The imidazo[1,2-a]pyridine core was constructed through a condensation between 2-aminopyridine analogues and arylglyoxals. Additionally, a new approach to the synthesis of benzylglyoxals was introduced. The imidazo[1,2-a]pyridines display moderate antioxidant activities at a low micromolar level in 2,2-diphenyl-1-picrylhydrazyl (DPPH).     

The mass spectra of some 1H-imidazo[1,2-a]pyrrolo[3,2-e]pyridines

We report here the mass spectral fragmentations of some derivatives of a new heterocyclic system 1H-imidazo[1,2-a]pyrrolo[3,2-e]pyridine. These compounds combine structural features of 1H-pyrrolo[2,3-b]pyridines and imidazo[1,2-a]pyridines, but follow fragmentation pathways similar to the former.     

Convenient synthesis of fused heterocycles from α-ketohydroximoyl chlorides and heterocyclic amines

Nitroso derivatives of imidazo[1,2-a]pyridine ( 11, 13, 14 ), imidazo[1,2-a]pyrimidine ( 15 ), imidazo[1,2-a]pyrazine ( 16 ), imidazo[1,2-b]pyrazole ( 17 ), and imidazo[1,2-b]-1,2,4-triazole ( 19 ) were obtained in good yields from α-ketohydroximoyl chlorides 3 and 2-aminopyridines ( 4–6 ), 2-aminopyrimidine ( 7 ), 2-aminopyrazine ( 8 ), 5-amino-3-phenylpyrazole ( 9 ), and 3-amino-2H-1,2,4-triazole ( 10 ), respectively. Under different conditions, the reaction of 3 with 3-amino-2H-1,2,4-triazole ( 10 ) and 2-aminopyrazine ( 8 ) afforded the noncyclized substitution products 18 and 22 , respectively. The structures of the products were assigned and confirmed on the basis of their elemental analyses, spectral data, and alternate synthesis wherever possible.     

Synthesis of azinoazole structural isomers by photocyclization

Irradiation of 2-chloro-N-(pyridin-2-yl)pyridin-3-amine and N-(2-chloropyridin-3-yl)-4,6-dimethyl-pyrimidin-2-amine in aqueous-alcoholic solution gave new azinoazole derivatives, 6-chlorodipyrido-[1,2-a:5′,4′-d]imidazole and 1,3-dimethylpyrido[3′,2′:4,5]imidazo[1,2-a]pyrimidine, respectively.     

Synthesis and properties of cyanomethyl derivatives of imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyridine,imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrimidine,and imidazo[2,1-<Emphasis Type="Italic">b</Emphasis>]thiazole

2-Cyanomethyl derivatives were obtained of imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine, and imidazo[2,1-b]thiazole, and their reactivity was investigated by an example of imidazo[1,2-a]pyridine: It was subjected to nitration, bromination, azo coupling and nitrosation. Acylation of the methylene group effected by amino acids esters with a subsequent addition of the amino group to the cyano group resulted in the formation of 5-amino-4-imidazo[1,2-a]-pyridin-2-yl-1-phenyl-1,2-dihydro-3H-pyrrol-3-one and 2-amino-1-ethyl-3-imidazol[1,2-a]pyridin-2-yl-4(1H)-quinolinone.     

Oxidative Recyclization of 4,6,7-Trichloro-5-hydroxy-2-(2-pyrimidylamino)-2,3-dihydrobenzo[b]furan

When 4,6,7-trichloro-5-hydroxy-2-(2-pyrimidylamino)- 2,3-dihydrobenzo[b]furan reacted with phenyliodoso diacetate, an unexpected oxidative recyclization was observed to give 3-(3,5,6-trichloro-1,4-benzoquinon-2-yl)imidazo[1,2-a]pyrimidine. 2-[N-2-(3,5,6-Trichloro-1,4-benzoquinon-2-yl)ethenylamino]pyrimidine is the intermediate product in the conversion.     

Polycyclic N-Heterocyclic Compounds,Part 77: Synthesis of [1]Benzothieno[3′,2′:2,3]oxepino[4,5-d]pyrimidines and Evaluation of Their Antiplatelet Aggregation Activity

Reaction of 3-(3-cyanopropoxy)[1]benzothiophene-2-carbonitrile with sodium hydride gave 5-amino-1,2-dihydro[1]benzothieno[3,2-d]furo[2,3-b]pyridine and 5-amino-2,3-dihydro[1]benzothieno[3,2-b]oxepin-4-carbonitrile. The latter compound served as a convenient scaffold for the synthesis of the new heterocycles [1]benzothieno[3′,2′:2,3]oxepino[4,5-d]pyrimidines and the parent 1,2,4,5-tetrahydro[1]benzothieno[2′,3′:6,7]oxepino[4,5-e]imidazo[1,2-c]pyrimidine heterocyclic system. The new compounds described in this report were evaluated as inhibitors of platelet aggregation in vitro.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Synthesis of nitrogen heterocycles underlain by application of 3-(4-Acetyl[phenyl)-2H-coumarin

3-(4-Acetylphenyl)-2H-chromen-2-one was obtained from 4-acetylphenyldiazonium chloride in the conditions of Meerwein reaction. Reactions of 3-[4-(2-bromoacetyl)phenyl]-2H-chromen-2-one with pyridine, 4-methylpyridine, quinoline, benzo[f]quinoline, and triphenylphosphine afforded quaternary salts, and with thioacetamide, thiourea, 2-aminopyridine, 2-aminopyrimidine, and 6-aminopurine provided the corresponding derivatives of thiazole, imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine, imidazo[2,1-i]purine. In the reaction of the same bromo derivative with thiosemicarbazide and aromatic aldehydes a thiazole ring is built and the corresponding hydrazones are formed.