Heteroaromatization with ketene dithioacetals: Part I. Synthesis of some novel 5-amino-1-(1,3,4-thiadiazol-2-yl) and 1-(1,3,4-thiadiazin-2-yl)pyrazole-4-carbonitriles

Abstract

Ketene dithioacetals [5][6][7][8][9][10][11][12][13][14] are one of the most common starting materials for the synthesis of pyrazoles. The reactions of ketene dithioacetals 1a,b with thiocarbohydrazide or thiosemicarbazide in hot ethanol afford the corresponding pyrazole derivatives 2a-d, respectively (Scheme 1). In addition, the syntheses of 2a-d could also be achieved through hydrazinolysis or ammonolysis of pyrazolyldithio-carbonate 3a,b, Scheme 1.

Chemistry and Tautomerism of Coupling Products of Diazotised Sulfamethoxazole with some Compounds Containing an Active Methylene Group

“…

In a continuation of our previous work 11,12 on the synthesis of pyrazole-dithiocarboxylates, we report here several new approaches to these derivatives.Diazotisation of p- [(5-methylisoxazol-3-yl)aminosulfonyl]aniline 1 followed by coupling with ethyl acetoacetate or ethyl benzoylacetate in ethanol in the presence of sodium acetate afforded the corresponding arylazo-β-ketoester derivatives 2a and 2b, Scheme 1.The structures of 2a and 2b were confirmed on the basis of elemental analyses and spectral data. 1 H-NMR spectra showed that the products 2a and 2b exist in DMSO-d 6 as an equilibrium mixture of three tautomeric forms 2A-C, Scheme 2, as 1 H-NMR for 2a revealed three signals for one proton at δ 7.66, 11.35 and 11.58 ppm where for 2b these signals appear at δ 7.55, 11.32 and 11.48 ppm.

…”

“…In a continuation of our previous work 11,12 on the synthesis of pyrazole-dithiocarboxylates, we report here several new approaches to these derivatives.…”

Substituted Pyrazoles and Their Heteroannulated Analogs—Recent Syntheses and Biological Activities

“…When pyrazolylcarbothiohydrazide 155 was treated with formic acid or triethyl orthoformate, it gave 3-methylsulfanyl-1-(1,3,4-thiadiazolyl-2-yl)pyrazolo[3,4- d ]pyrimidin-4(5 H )-one 156 ( Scheme 80 ) [ 118 ].…”

Reactions of ketene dithioacetal for a new versatile synthesis of 4,5-substituted 3-aminothiophene-2-carboxylate derivatives

“…[3] Ketene dithioacetals could be used in reactions with various nucleophiles leading to synthesis of a variety of nitrogen heterocycles like pyridines, pyridones, pyrimidines, quinolines, pyrroles, pyrazoles and imidazoles. [1,2,[5][6][7][8][9][10][11] They are used in the synthesis of sulfur containing heterocycles like thiophenes, thiopyrans and other bioactive molecules like cyclopentanoids, polyenes, etc. [1][2][3][4][5][6][7][8][9][10][11] Thiophenes form a major class of bioactive heterocycles.…”

“…[1,2,[5][6][7][8][9][10][11] They are used in the synthesis of sulfur containing heterocycles like thiophenes, thiopyrans and other bioactive molecules like cyclopentanoids, polyenes, etc. [1][2][3][4][5][6][7][8][9][10][11] Thiophenes form a major class of bioactive heterocycles. They show a broad spectrum of biological response such as antibacterial, [12][13][14] anti-leishmanial, [1] antifungal, [1,[12][13][14][15] antimicrobial, [12][13][14][15] antitumor, [16,17] anticancer, [16,17] antiinflammatory, [13,14] antiproliferative, [18] molluscicidal [19] and anticonvulsant activity.…”