Mohamed A. A. Elneairy

Synthesis of Thiazole, Triazole, Pyrazolo[3,4-b]-Pyridinyl-3-Phenylthiourea, Aminopyrazolo[3,4-b]Pyridine Derivatives and Their Biological Evaluation

Abstract The pyrazolopyridine derivatives 1a,b reacted with phenylisothiocyanate (2), nitrous acid and cinnamonitrile derivatives 5a,b to afford the corresponded pyrazolo[3,4-b]-pyridinyl-3-phenylthiourea derivatives 3a,b, 3-diazotized aminopyrazolo[3,4-b]-pyridine derivatives 4a,b and Schiff bases 7a-d in a respective manner. Compounds 3a,b, 4a,b and 7a,d were taken as the starting materials for the present study owing to the presence of more than one active site. Compounds 3a,b reacted with the halogen-containing reagents e.g. 11a,b, 13 and 15 to give the corresponded thiazole derivatives 12a-d, 14a,b and 16a,b respectively. Compounds 4a,b coupled with the active hydrogen-containing reagents 17a,j to afford the corresponding 3-hydrazino derivatives 18a-t which could be cyclized to give the corresponding triazines 19a-t respectively. Compounds 7a-d reacted with thioglycolic acid (9) to give the corresponding thiazole derivative 10a-d in a good yield. The assigned structures of the newly synthesized compounds are based on their elemental analyses. IR. 1H NMR and mass spectra. The biological activity of some of these compounds was tested.

Reactions and characterization of pyridin-6-one-2-thione and 3-diazotized amino-4-hydroxypyrazolo-[3,4-b]pyridin-6-one

Several pyrido[2,1-b]thiazines and thiazolo[2,3-a]pyridines were synthesized by reactions of cinnamonitriles with appropriate halocarbonyl compounds. Hydrazones of 3-diazotized aminopyrazolo[3,4-b]pyridinones were synthesized by coupling of their corresponding diazonium salts with several active methylene reagents. The obtained hydrazones were cyclized in refluxing ethanol containing a catalytic amount of triethylamine to afford the corresponding pyrazolopyridotriazines. All structures were established by considering the data of elemental analyses, IR, 1H-NMR, and mass spectra.

Cyanothioacetamide in Heterocyclic Chemistry: Synthesis of Thiopyran, Pyridinethione, Thienopyridine, Pyridothienotriazine and Pyridothienopyrimidine Derivatives

Abstract Cyanothioacetamide (1) reacted with α- and β-naphthaldehyde 2a,b to afford the corresponding 3-naphthyl-2-thiocarboxamidopropenonitriles 3a,b. Compounds 3a,b structures could be elucidated via their reactions with acrylonitrile, ethyl acrylate (4a,b). N-arylmaleimides 6a-c and ethyl acetoacetate (8). The isolated products could be represented as the thiopyran, thiopyranopyrrolidine and pyridinethione derivatives 5a-d, 7a-f and 9a,b respectively. Pyridinethiones 9a,b had been used as the starting materials in the present study in addition to the next ones to synthesize several new thienopyridines, pyridothienotriazine and pyridothienopyrimidines 12a-f, 15a,b, 16b, 17–19a,b respectively through their reactions with the corresponding reagents. All structures of the newly synthesized heterocyclic compounds were established on the basis of the data of IR, 1H NMR and elemental analyses.

Synthesis and antimicrobial evaluation of new pyridine, thienopyridine and pyridothienopyrazole derivatives

The reaction of thiocyanoacetamide (1) with α,β-unsaturated ketones2a,b resulted in the formation of the corresponding newly synthesized 1(H)-pyridinethione derivatives3a,b. Compounds3a,b were used as synthons for the preparation of 2-S-alkyl-, 2-S-aryl, 2-S-acetamidopyridine, thieno[2,3-b]pyridine and pyrazolo[3,4-b]pyridine derivatives via a wide range of reactions with different reagents. The antimicrobial activity of some of the newly synthesized compounds was tested. Compounds3a, 11a, 15a, and19a,b were found to be the most active ones.

Reactions of Cyanothioacetamide: Synthesis of Several New Thioxohydro-pyridine-3-carbonitrile and Thieno[2,3-b]pyridine Derivatives

Cyanothioacetamide (f 1) reacted with α,β -unsaturated carbonyl compounds 2a–d to afford thioxohydropyridine-3-carbonitriles 5a–d, which were used as the starting materials for the preparation of several thienopyridines via their reactions with active halogen-containing compounds, e.g., 2-bromo-1-phenylethanone (7a), 2-bromo-1-p-tolyl-ethanone (7b), chloroacetone (10a), α -chloroacetylacetone (10b), and chloroacetic acid ethyl ester (13). The structure of the newly synthesized heterocyclic compounds were established based on the data of elemental analyses, IR, 1 H NMR, and mass spectra.

REACTIONS WITH CYANOTHIOACETAMIDE AND ITS DERIVATIVES : SYNTHESIS AND CHARACTERIZATION OF SEVERAL NEW PYRIDINE AND ANNELATED PYRIDINE DERIVATIVES

Abstract Several new pyridines and annelated pyridines were synthesised via the reactions of some pyridinethiones with a variety of activated halogenomethyl containing reagents and hydrazines. Structures were established on the basis of elemental analysis and spectral data.

REACTIONS WITH CYANOTHIOACETAMIDE AND ITS DERIVATIVES : SYNTHESIS AND REACTIONS OF SEVERAL NEW THIENO- AND AZOLOPYRIDINE DERIVATIVES

Abstract Several new thieno- and azolopyridine derivatives were synthesized via a new route by reaction of some new di- and tetrahydropyridine thiones with different halogeno-ketones and halogeno-esters. Structures were elucidated by elemental analysis and spectral data.

Thieno[2,3-b]pyridine-2-carbohydrazide in Polyheterocyclic Synthesis: The Synthesis of Pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine, Pyrido[3′,2′:4,5]thieno[3,2-d][1,2,3]triazine, and Pyrazolyl, Oxadiazolylthieno[2,3-b]pyridine Derivatives

Pyrdine-2(1H)-thione 1 reacted with ethyl chloroacetate 2 to give 2-S-ethoxy-carbonylmethylpyridine derivative 3, which could be cyclized into thieno[2,3-b]-pyridine-2-carbohydrazide derivative 5 by boiling with hydrazine hydrate. The latter compound reacted with cinnamonitrile derivatives 6a, b, triethylorthoformate, formic acid, dimethylformamide-dimethylacetal, and diethyl carbonate to give the corresponding shiff base 7a, b and pyrido[3′,2′;-4,5]thieno[3,2-d]pyrimidine derivatives 10–13 in respective manner. On the other hand, compound 5 also reacted with carbondisulphide and phenyl isothiocyanate to afford the corresponding 2-(1,3,4-oxadiazolo-2-yl)thieno[2,3-b]pyridine derivatives 18 and 22. Finally, compound 5 reacted with some β-dicarbonyl compounds, such as ethyl acetoacetate, acetylacetone and ethyl β-arylazoacetoacetate, to yield the corresponding 2-(pyrazol-1-yl-carbonyl)thieno[2,3-b]pyridine derivatives 24, 25, and 27 respectively.

Synthesis of Novel Bis-2-(1,3,4-thiadiazolin-3-ylphenoxy) Alkane Derivatives

A novel synthesis of bis(thiadiazolin-3-yl)ethers 6a-f and bis(thiadiazolin-2-on-3-yl)ethers 10a-f via the reaction of the bis (diazonium) salts 2a-c with the appropriate y -thiocyanatoacetophenone derivatives 4a-c .

Pyrido[2,3-d]pyrimidine-2,7-dithiol in heterocyclic synthesis: Synthesis and characterization of several new fused pyridopyrimidine heterocycles

Pyridine-2(1H)-thione 1 reacted with phenyl isothiocyanate to give pyrido[2,3-d]pyrimidine derivative 3. Compound 3 reacted with halogen containing compounds 4a–d and methyl iodide in dimethylformamide/potassium hydroxide solution at room temperature to give 2,7-bisalkylthiopyrido[2,3-b]pyrimidine derivatives 5a–d and 9, respectively. Compounds 5a–d could be cyclized into thienopyrido[2,3-d]pyrimidine derivatives 6a–d by boiling with ethanolic potassium hydroxide solution. Compound 6a reacted with acetic anhydride or formic acid and gave the corresponding pyrimido[4″,5″:4′,5′]thieno[3′,2′:5,6]pyrido[2,3-d]pyrimidine derivatives 8a,b. Compound 9 reacted with hydrazine hydrate to yield pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidine derivative 11 which could be reacted with nitrous acid and dimethylformamide-dimethylacetal (DMF-DMA) and gave the final isolable products corresponding to the pyrazolo[4′,3′:5,6]pyrido[2,3-d]tetrazolo-[5,1-b]pyrimidine and pyrimido[1″,2″:1′,5′]pyrazolo[4′,3′:5,6]pyrido[2,3-d]1 2 4triazolo-[4,3-b] pyrimidine derivatives 13 and 17, respectively. Compound 11 also reacted with some β-dicarbonyl compounds such as acetylacetone (18) and ethyl acetoacetate (20) to yield the corresponding pyrimido[1″,2″:1′,5′]pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidine derivatives 19 and 21, respectively. Finally, compound 11 reacted with chloroacetyl chloride (22) to give the corresponding imidazo[1″′,2″′:1″,5″]pyrazolo[4″,3″:5′,6′]pyrido[3′,2′:5,6]pyrimido[2,1-c]1 2 4triazine derivative 23.