Zaghloul E. Kandeel

Synthesis and reactivity of 3-(benzothiazol-2-yl)-3-oxopropanenitrile

The versatile, hitherto unreported 3-(benzothiazol-2-yl)-3-oxopropanenitrile (3) was prepared by two convenient routes: either by the reaction of ethyl 2-benzothiazolecarboxylate (1) with acetonitrile in the presence of sodium hydride or by treatment of 2-bromoacetylbenzothiazole (2) with potassium cyanide. Reaction of 3 with heterocyclic diazonium salts furnished the corresponding hydrazones 6, 7 and 13, respectively. The latter products underwent intramolecular cyclization into the corresponding pyrazolo[5,1-c]-1,2,4-triazine, 1,2,4-triazolo[5,1-c]-1,2,4-triazine and 1,2,4-triazolo[4,3-a]benzimidazole derivatives 8, 9 and 14, respectively, upon boiling in pyridine. Compound 3 coupled also with diazotized aromatic amines and gave the corresponding arylhydrazones 16a-c which undergo cyclocondensation with hydrazine and phenylhydrazine to afford the pyrazole derivatives 17a-c and 18a-c, respectively. Cyclocondensation of compound 3 with hydrazine derivatives afforded the corresponding aminopyrazoles 19 and 20, respectively in good yields.

Facile synthesis of novel polysubstituted thiopene and 1,3,4-thiadiazole derivatives

Abstract 3-(Benzothiazol-2-yl)-3-oxopropanenitrile ( 1 ) reacts with phenylisothiocyanate in the presence of potassium hydroxide followed by addition of the hydrazonoyl bromides 2a-c to afford the novel 1,3,4- thiadiazole derivatives 6a-c via the intermediate 4 . Reaction of 4 with 2-bromoacetylbenzothiazole ( 3 ) furnished the new polysubstituted thiophene 13 . Treatment of the latter product with aromatic diazonium salts resulted in the formation of 2-arlazothiophene derivatives 16a-c . A suggested mechanisms of the investigated reactions were presented.

Nitriles in Heterocyclic Synthesis: The Reaction of 2-Thiocarbamoyl Cinnamonitriles with Active Methylene Reagents

Abstract Substituted pyridin-2-thiones, 2-pyridones, thiopyrans and pyranoazoles could be synthesized via the reaction of 2-thiocarbamoyl cinnamonitriles with some active methylene reagents.

Cationic Polar Cycloaddition with Anodically Prepared a-Tri- and a-Difluoromethylated N,O-Acetals: Preparation of Fluoromethylated Tetra- and Dihydroquinoline Derivatives

Anodically prepared α-tri- and α-difluoromethylated N,O-acetals readily underwent [4 + +2] type polar cycloadditions with styrenes and phenylacetylene in the presence of a Lewis acid to provide the corresponding fluoromethylated tetra- and dihydroquinoline derivatives

Heterocyclic synthesis via enaminones: Regioselective synthesis of some novel pyrazole, isoxazole, pyrimidine, pyrido[1,2‐a]benzimidazole and pyrazolo[1,5‐a]‐pyrimidine derivatives

2-Acetylbenzothiazole (1) reacts with dimethylformamide dimethylacetal (DMF-DMA) to afford the enaminone 2. Compound 2 reacts regioselectively with some nitrilimines 5a–d and nitrile oxides 6b–d to afford the novel pyrazole and isoxazole derivatives 11a–d and 12b–d, respectively, which react with hydrazine hydrate to give the new pyrazolo[3,4-d]pyridazine and isoxazolo[3,4-d]pyridazine derivatives 13a–d and 14b–d, respectively. The enaminone 2 reacts with 1H-benzimidazole-2-acetonitrile (17) to afford the pyrido[1,2-a]benzimidazole derivatives 19. Compound 2 reacts also with 5-amino-3-phenylpyrazole (20) and with guanidine to afford the new pyrazolo[1,5-a]pyrimidine and the 2-aminopyrimidine derivatives 22 and 24, respectively.

Polyheterocyclic ring systems with bridgehead nitrogen atoms: a facile route to some novel Azolo-1,2,4-triazine derivatives

The synthesis of the entitled azolo-1,2,4-triazines via the reaction of some functionalized thiazole derivatives with several heterocyclic diazonium salts is described.

Activated nitriles in heterocyclic synthesis: reaction of cyanogen bromide with some functionally substituted enamines

Novel procedures for the synthesis of pyrazolo[4,3-c]-1,2,4-triazines and 2-bromopyrimidine derivatives have been developed via reaction of cyanogen bromide with some substituted enamines.

CONVENIENT SYNTHESIS OF SOME NEW 1,3,4-THIADIAZOLE AND 1,3,4-SELENADIAZOLE DERIVATIVES

Abstract The novel 1-aryl-5-(benzothiazol-2-yl)carbonyl-2-imino-1,3,4-thiadiazoles 7a-c and their selenium analogues 8a-c were prepared in high yields by coupling of 2-thiocyanatoacetylbenzothiazole 3 or its selenium analogue 4 with aromatic diazonium salts. The same products were alternatively obtained from the reaction of the hydrazonoyl bromides 2a-c with potassium thiocyanate and with potassium selenocyanate, respectively. Reactions of 7a-c and 8a-c with acetic anhydride and with benzoyl chloride afforded the corresponding N-acetyl derivatives 13a-c and 14a-c and N-benzoyl derivatives 15a-c and 16a-c, respectively.

Enaminones in Heterocyclic Synthesis: A Novel Route to Polyfunctionalized Substituted Thiophene, 2,3-Dihydro-1,3,4-Thiadiazole and Naphtho[1,2- b ] Furan Derivatives

The enaminones 1a , b reacted with phenylisothiocyanate to afford the thioanilides 2a , b . The latter could be utilized to synthesize several new polysubstituted thiophenes 9a-f , and 1,3,4-thiadiazoles 12a-f .

THE REACTION OF w- THIOCYANATOACETOPHENONES WITH HYDRAZINES

Abstract w-Thiocyanatoacetophenones la, b react with hydrazine hydrate to yield bis[4-aryl-5-hydro-δ3,4-thiazol- 2-ylidine] azines 2a, b . Compounds 1a, b react with phenyl hydrazine to yield 1-phenyl-6-phenylazo- 3,6-diaryl-l,4,5,6-tetrahydropyridazines 5a, b respectively. The phenylhydrazone of la was obtained via indirect method.