of Some New Heterocyclic Schiff Bases Derived from Thiocarbohydrazide

Abstract

The reaction of pyrazolobenzothienopyrimidine-3-carbaldehyde 1 with thiocarbohydrazide afforded the Schiff's base 3. The latter compound reacted with some electrophilic reagents to give 1,2,4-triazoles 4-6 and 1,2,4-triazines 7-9. Treatment of compound 3 with 2-cyano-3,3-bis(methylthio)acrylonitrile gave the corresponding 5-amino-4-cyano-3-methylthiopyrazole derivative 11. The reaction of pyrazole 11 with carbon disulfide afforded dithioxopyrazolopyrimidine 12. Acylation of compound 11 by using acetic anhydride yielded acetamide 13. On the other hand, the cyclocondensation of pyrazole 11 with acetic anhydride in pyridine yielded pyrazolopyrimidine derivative 14. The reactivity of compound 11 towards formamide and phenylisothiocyanate to give the pyrazolopyrimidines 15 and 16 was studied. The newly synthesized compounds were screened for their antimicrobial activity.

Green One-pot Synthesis of Novel Polysubstituted Pyrazole Derivatives as Potential Antimicrobial Agents

“…1 H and 13 C NMR spectra were recorded at 400 and 100 MHz, respectively, on a Bruker FT-NMR Ultra Shield-400 spectrometer. Elemental analyses were performed for C, H and N on a Thermo Finnigan Flash EA microanalyzer.…”

“…33 Three-component reaction in 0.5 g of each of these three DESs at room temperature have resulted in the Schiff bases and benzylidenemalononitriles as the major products (Entries 7, 9, 11), pyrazoles were obtained in 35-40% yields due to the increase of temperature to 80 °C (Entries 8, 10, 12). One-pot twostep process was screened according to route b. Two-step procedure was carried out in all DESs, the increase in molar ratios of glycerol reduced the product yield (Entries [13][14][15][16][17][18]. This can be caused by the higher pH of DES1.…”

“…The first stage reaction did not proceed completely at room temperature or at higher temperature even after 8 h, due to the lack of appearance of the intermediary benzylidenemalononitriles in the reaction media. Therefore, the next stage reaction of unconsumed reagents especially aldehydes with hydrazine was inevitable under these conditions (Entries 13,15,17). Adding water to achieve the final DES1/H 2 O ratios of 1:2, 1:1 and 3:1 (w:w) has improved reaction time and product yield, the condensation reaction of malononitrile with aldehyde 113.67-117.37 ppm.…”

“…One of the synthesized 1,2,4-triazines could block the growth of all selected microorganism. 13 Various methods were proposed for the synthesis of pyrazole and their analogues. [14][15][16][17] In this regard, a solution of the appropriate triethylamine in 1,4-dioxane efficiently catalysed synthesis of pyridine, thiophene and 4H-pyrane Similar procedures were designed to prepare pyrazole derivatives.…”

The Lock is the Key: Development of Novel Drugs through Receptor Based Combinatorial Chemistry

“…19 In addition to the fast and reversible nature of condensation between amines and aldehydes to imines, reversible imine formation is very convenient for drug discovery because it yields a Schiff base, a very common motive in metabolites and biologically active compounds. 30,31 To detect products by HPLC, they "locked-in" the equilibrium by irreversible reduction of imines to corresponding amines using Na-BH 3 CN to fix the composition of the library prior to detection.…”