Yusria R. Ibrahim

SYNTHESIS OF PYRIDAZINE AND 1,3-THIAZINE DERIVATIVES VIA CT-COMPLEXATION BETWEEN THIOSEMICARBAZIDES AND TETRACYANOETHYLENE

Abstract Intermolecular charge transfer (CT) complexes of aromatic aldehyde thiosemicarbazones with some π-acceptors such as 7,7,8,8-tetracyanoquinodimethane, 2-(dicyanomethylene)indane-1,3-dione and 9-dicyanomethylene-2,4,7-trinitrofluorene have been studied spectrophotometrically. Aromatic aldehyde thiosemicarbazones, and thiosemicarbazide reacted with tetracyanoethylene via CT-complex formation to give 1,3-thiazine and pyridazine derivatives.

Synthesis and antibacterial activity of 4-aryl-2-(1-substituted ethylidene)thiazoles.

(E)‐4‐Aryl‐2‐[2‐(1‐substituted ethylidene)hydrazinyl]thiazoles and (Z)‐3‐substituted‐4‐aryl‐2‐[(E)‐(1‐phenylethylidene)hydrazono]‐2,3‐dihydrothiazoles were synthesized by the reaction of (substituted ethylidene)hydrazinecarbothioamides with ω‐bromoacetophenones. The characterization of this new class of compounds was performed using different spectroscopic tools. The structure of (Z)‐3‐benzyl‐4‐(4‐bromophenyl)‐2‐[(E)‐(1‐phenylethylidene)hydrazono]‐2,3‐dihydrothiazole 6e was unambiguously confirmed by single‐crystal X‐ray crystallography. Compounds 5a–e, 5i, 6e, 6g, and 6i were screened for their in vitro antibacterial activity against different strains of microorganisms; most of the tested compounds exhibited promising antibacterial activity against some organisms compared to ciprofloxacin and sulbactam penicillin. Compounds 5e, 5i, 6e, 6g, and 6i exhibited several‐fold significant antibacterial activity against the Gram‐positive bacteria Staphylococcus aureus, better than ciprofloxacin, with minimum inhibitory concentration values ranging from 0.05 to 0.4 µg/mL. The rest of the tested compounds gave significant antibacterial activities against different Gram‐negative bacterial strains.

Synthesis of 1,3-thiazin-2-ylidene-substituted hydrazides via reaction of N -substituted-hydrazino-carbothioamides with 1,4-diphenylbut-2-yne-1,4-dione

1,4-Diphenylbut-2-yne-1,4-dione reacts with N-substituted-hydrazino-carbothioamides to form the corresponding N’-6-benzoyl-4-phenyl-2H-1,3-thiazin-2-ylidene]-substituted-hydrazides.

Indazole, oxathiadiazole, and thiadiazine derivatives from thiosemicarbazides

4-Substituted thiosemicarbazides 1a–c reacted with 2,3-dicyano-5,6-dichloro-1,4-benzoquinone (DDQ, 2), 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL-p, 6) and 2,3-dichloro-1,4-naphthoquinone (DCHNQ, 7) in ethyl acetate with admission of air and form the derivatives of 1,5,2,3-oxathiadiazole 8a–c, indazole 9a–c, 1,3,4-thiadiazine-6-one 10a–c, 1,3,4-thiadiazaphenanthren-9-one 11a–c, naphtho[1,2-e:4,3-è]bis1 3 4thiadiazine 12 and dibenzo[b,i]thianthrene-5,7,12,14-tetraone 13. A rationale for the conversions observed is presented.

Oxadiazole, oxadiazine, oxadiazepine, pyrazole and tetrazole derivatives from substituted carbohydrazides

The condensation of substituted carbohydrazides 1a–e with a series of electron-poor compounds such as dimethyl but-2-ynediolate (2), 1,4-diphenylbut-2-yne-1,4-dione (3), 1,4-diphenylbut-2-ene-1,4-dione (4), and diethyl diazene-1,2-dicarboxylate (5) gave the derivatives of 1,3,4-oxadiazepine, 1,3,4-oxadiazinylacetate, (1,3,4-oxadiazolylidene) ethanone, dibenzoylpyrazole and tetrazolecarboxylate. The reaction mechanisms described the products formation are discussed.

Synthesis of spiro(cyclohexa-diene-pyrazolo[1,5-a]pyrimidine-4-ylidene)-malononitrile derivatives

The reaction of 4-substituted aryldiazenyl-1H-pyrazole-3,5-diamines with 7,7′,8,8′-tetra-cyanoquinodimethane gave 2-(2′,7′-diamino-6′-cyano-3′-(aryldiazenyl)-4′H-spiro(cyclohexa[2,5]-diene-1,5′-pyrazolo[1,5-a]pyrimidine-4-ylidene) malononitriles in 63–79% yield, while, by reaction of 2-aminobenzimidazole with 7,7′,8,8′-tetracyanoquinodimethane, 2-(3′-amino-4′-cyano-6′H-spiro-(cyclohexa[2′,5′]diene-1,5′-benzo(d)-imidazo[1,2-a]pyrimidine)-4-ylidene)malononitrile was formed in 71% yield. Rationales for these transformations are presented.

Synthesis of imidazo- and pyrazolothiadiazoles from dithiobiureas and dimethyl ethynedicarboxylate

Microwave irradiation of 1-substituted-2, 5-dithiobiureas and 1, 6-disubstituted-2, 5-dithiobiureas with dimethyl ethynedicarboxylate gave methyl 2-{6-oxo-2-(substituted amino)imidazo-[2, 1-b][1, 3, 5]thiadiazol-5(6H)-ylidene} acetate and methyl 7-oxo-1, 3-bis(substituted imino)-3, 7-dihydro-1H-pyrazolo[1, 2-c][1, 3, 4]thiadiazole-5-carboxylate. Rationales for these transformations are presented.

Reactions of Substituted Carbohydrazides with Electron-poor Olefins

Substituted carbohydrazides 1a - e reacted with ethenetetracarbonitrile (2) in dimethylformamide with formation of diacylhydrazines 4a - e and 5-amino-1-substiuted pyrazole-3,3,4-tricarbonitriles 5a - e. On the other hand, 1a-c reacted with diethyl (E)-2,3-dicyanobutenedioate (3) to give oxadiazinone and pyrazolone derivatives 12a - e and 13a - e, respectively.