Pratibha Srivastava

Chloropyrimidines as a new class of antimicrobial agents.

In the course of our investigations of pyrimidines as antimycotic agents, we have identified a sub-class, with significant in vitro activity against mycobacteria. The salient feature of these pyrimidine derivatives (3a-o and 7a,b) is their appended aryl, heteroaryl and alkylthio substituent at position 6 and also alkylthio substituent at position 2. The rational design, synthesis, and evaluation of the in vitro antibacterial activity against six pathogenic bacteria including virulent and non-virulent strains of Mycobacterium tuberculosis is described. Some of the synthesized compounds (3c, 3h, 3i, 3o) have displayed only potent in vitro antimycobacterial activity with MIC of 0.75 microg/mL except 3i which also demonstrated activity against Escherichia coli at 12.5 microg/mL concentration. Only two compounds, 3a and 3b, demonstrated antibacterial activity against Pseudomonas aeruginosa and E. coli with MIC 12.5 microg/mL. All the synthesized compounds were also evaluated for their antimycotic activity against five pathogenic fungi but only some of them 3j-n and 7a,b were found most potent against Aspergillus fumigatus and Trichophyton mentagrophytes.

Synthesis of bridgedhead azolo[3,2-a]pyrimidines and imidazo[2,1-b]thiazines through ring transformation of 2H-pyran-2-ones

Suitably functionalized 3-carbomethoxy/cyano-2H-pyran-2-ones are excellent synthons for the synthesis of arenes and heteroarenes of therapeutic importance. The compounds 6-aryl-3-cyano-4-methylsulfanyl-2H-pyran-2-ones have been transformed into bridgedhead azolopyrimidines and imidazothiazines through thermal and base-induced ring transformation reactions with aminoazoles and imidazolidin-2-thiones, respectively.

An Expeditious Synthesis of Heteroarenes through Carbanion‐Induced Ring Transformation Reactions of Suitable Functionalized Pyran‐2‐ones

Pyrazolo[1,5-a]pyridines (3) and pyrano[4,3-d]pyrazolo[1,5-a]pyridines (4) have been synthesized from the reaction of pyran-2-one (1) and 5-aryl-3-cyanomethyl-1H-pyrazole (2) through carbanion-induced ring transformation reactions. A regioselective synthesis of highly functionalized polysubstituted pyrazolo[1,5-a]pyridines (6, 7) has also been achieved from the reaction of 2 with polarised ketene dithioacetals (5) and arylidenemalononitrile, respectively. An analogous reaction of 1 with 2-cyanomethyl-1H-benzimidazole (8) has also afforded the fused heterocycles 9 and 10. The cyano function in 9 has been exploited for acid-catalysed cyclization with thiosemicarbazide to obtain 11 in high yield.

5-Cyano-2-thiouracils and their derivatives: a new class of leishmanicides

Abstract Several 5-Cyano-6-substituted-2-thiouracils (1a–e) and their monocyclic (2,3,4,6) and bicyclic (5) derivatives have been prepared and evaluated for in vivo leishmanicidal activity against L. donovani in hamster.

Carbanion induced synthesis of pyrido[2,1-b] benzothiazoles through ring transformation reactions

3-Aryl-1-[(E)-cyanomethylidene]-1H-pyrido[2,1-b]benzothiazole-4-carbonitriles (3) and the polysubstituted pyrido[2,1-b]benzothiazoles (8, 9) have been prepared from the reaction of 2-benzothiazoleacetonitrile (2) with 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitrile (1) and the ketenedithioacetals (6, 7), respectively.

One-pot synthesis of unsymmetrical biaryls from suitably functionalized 2H-pyran-2-ones through carbanion-induced ring-transformation reactions

An innovative synthesis of unsymmetrical biaryls (2,6) with electron-acceptor and electron-donor substituents through carbanion-induced C–C bond formation from 6-aryl-3-cyano-4-methylthio-2H-pyran-2-ones (1) and 4-sec-amino-6-aryl-2H-pyran-2-ones (5), using aliphatic ketones as a source of carbanion, is delineated and illustrated. However, a reaction of pyran-2-ones (1) with aromatic ketones failed to yield any desired product and in lieu a new compound isolated was characterized as the corresponding (4,6-diarylpyran-2-ylidene)acetonitrile (3). The structure of two representative compounds 5h and 6q has been confirmed by single-crystal X-ray diffraction analysis.

A facile access to the synthesis of functionalised unsymmetrical biaryls from 2H-pyran-2-ones through carbanion induced C–C bond formation

A convenient synthesis of highly functionalised biaryls 3 and 6 has been delineated through carbanion induced C–C bond formation from 6-aryl-3-cyano-4-substituted-2H-pyran-2-ones (1, 4) and acetone. Extension of this reaction, using aromatic ketones led to (4,6-diarylpyran-2-ylidene)acetonitrile (7) in lieu of the anticipated 2,4-diaryl-6-methylthiobenzonitrile (8). The structure of 2-methyl-6-methylthio-4-(3,4-methylenedioxyphenyl)benzonitrile (3f) was ascertained by single crystal X-ray diffraction analysis and displayed a variety of weak interactions, responsible for the stability and packing of the molecule in the crystalline state.