Bharati V. Badami

Transformation of the sydnone ring into oxadiazolinones. A convenient one-pot synthesis of 3-aryl-5-methyl-1,3,4-oxadiazolin-2-ones from 3-arylsydnones and their antimicrobial activity.

3-Arylsydnones (Ia-u) have been converted into the corresponding 3-aryl-5-methyl-1,3,4-oxadiazolin-2-ones (IIIa-u) by a single-step reaction with bromine in acetic anhydride. In the preliminary screening of all these compounds, the halogen-substituted derivatives have shown antimicrobial activities equal to those of the standard drugs used.

Mesoionic compounds: An Unconventional Class of Aromatic Heterocycles

Mesoionic compounds are distinct types of heterocycles which belong to the class of nonbenzenoid aromatics. Sydnone, the representative mesoionic compound has been extensively studied because of its unusual structure, chemical properties and synthetic utility. Sydnone is used as a versatile synthon in heterocyclic synthesis. This article gives a brief account of the comparative studies of the structural features of mesoionic compounds and other heteroaromatic systems. Some synthetically useful tandem reactions of sydnones are also discussed.

Curtius rearrangement reactions of 3-(4-azidocarbonyl) phenylsydnone. Synthesis of 4-(sydnon-3-yl) phenyl carbamates, N-aryl-N′-[4-(sydnon-3-yl)] phenyl ureas and their antimicrobial and insecticidal activities

Abstract3-[4-(Azidocarbonyl)]phenylsydnone (2) obtained from 3-(4-hydrazinocarbonyl) phenylsydnone (1) on Curtius rearrangement with alcohols, water and amines afforded the corresponding carbamates (3a-h), 4,4′-(sydnone-3-yl) diphenyl urea (4) and 4-(heterocyclyl)phenyl ureas (5a-l). Compounds (5a-l) on one-pot ring conversion yielded the 1,3,4-oxadiazolin-2-one derivatives (6a-l), which on reaction with N2H4 gave the 4-amino-1,2,4-triazolin-3-ones (7a-l). All these compounds exhibited moderate antimicrobial activity against the few microbes tested. The carbamates have been found to be more toxic against fourth instar larvae ofAedes aegypti, in particular, then-butyl derivative (3e).

Synthetic utility of sydnones: synthesis of pyrazolines derivatized with 1,2,4-triazoles as antihyperglymic, antioxidant agents and their DNA cleavage study

Ring transformation of sydnone (1a–i) to 1,3,4-oxadiazoline-2-one (2a–i) was carried out using bromine in acetic anhydride. The compounds (2a–i) on heating with hydrazine hydrate gave 1,2,4-triazole (3a–i) in good yields. The structure of these unknown compounds was confirmed by IR, 1H NMR, MS and elemental analysis. Further, these compounds were evaluated for the extent of penetration into biological membranes (clogP) drug likeliness and finally drug score was calculated. The title compounds were also screened for their antihyperglycemic, DNA cleavage and antioxidant activity.

Sydnones as Masked Hydrazines for the Synthesis of 4‐Arylazo‐1,2‐dihydro‐pyrazol‐3‐one Derivatives

Abstract A simple and convenient one‐pot synthesis of 4‐(4‐chlorophenylazo)‐5‐methyl‐2‐aryl‐1,2‐dihydro‐pyrazol‐3‐ones (4a–j) has been carried out from 3‐arylsydnones (3a–j) by reaction with 2‐(4‐chlorophenyl)‐hydrazono‐3‐oxo‐butyric acid ethyl ester (2b). The 3‐arylsydnones are used as masked hydrazines in this reaction. Similarly, the 4‐arylazo‐2‐(7‐hydroxy‐4‐methyl‐2‐oxo‐2H‐chromen‐8‐ylmethyl)‐5‐methyl‐1,2‐dihydro‐pyrazol‐3‐ones (7a–j) were synthesized from 3‐[(7‐acetoxy‐4‐methyl‐8‐methylene)coumaryl]sydnone (5). All the newly synthesized compounds exhibited antimicrobial activity greater than the reference drugs used.

1,3-Dipolar cycloaddition reactions in heterocyclic synthesis. Synthesis of [1-[4-(thiazolyl/imidazothiazolyl/triazolyl)phenyl]-1H-pyrazole-3,4-dicarboxylate esters from 3-(4-acetylphenyl)sydnone

Cycloaddition of 3-(4-acetylphenyl)sydnone (1) with DMAD gave dimethyl 1-(4-acetylphenyl)-1H-pyrazole-3,4-dicarboxylate (2), which on bromination yielded the corresponding monobromoacetyl (3) and dibromoacetyl (4) derivatives. Both compounds 3 and 4 on reaction with thiourea and thioacetamide afforded the 2-amino- (5) and the 2-methyl- (6) thiazole derivatives respectively, while compound 3 on reaction with 2-aminothiazole gave the imidazothiazole 7. Compound 3 was converted into its azide (8), which on 1,3-dipolar cycloaddition with DMAD afforded the 1,2,3-triazole-4,5-dicarboxylate (9).

Chemical reactivity of 3-aryl-5-methyl-1,3,4-oxadiazolin-2-ones towards nitrogen nucleophiles. Part 1. One-pot ring conversion of 3-aryl-5-methyl-1,3,4-oxadiazolin-2-ones into 4-amino-2-aryl-5-methyl-2,4-dihydro-3H-1,2,4-triazal-3-ones

The ring transformation of 3-aryl-5-methyl-1,3,4-oxadiazolin-2-ones 1a–n into 4-amino-2-aryl-5-methyl-2,4-dihydro-3H-1,2,4-triazol-3-ones 3a–n, by reaction with hydrazine hydrate, is described. The products were screened for biological activity, and were found to be active against fungal strains.

N-(4-Acetyl­phenyl)-N′-[(4-sydnon-3-yl)­phenyl]­urea di­methyl­form­amide solvate

In the title compound, C17H14N4O4·C3H7NO, the dihedral angle between the planes of the sydnone ring and the attached benzene ring is 13.56 (8)°. The benzene rings are inclined at an angle of 21.02 (8)° with respect to one another. In the solid state, intermolecular N—H⋯O hydrogen bonds and weak intermolecular C—H⋯O interactions are observed.

Conformational analysis of cyclohexanes diastereoisomerism in disubstituted cyclohexanes

The cycloalkanes most commonly found in nature, viz., in some alkaloids, steroids and terpenoids contain six membered rings because they can exist in a completely strain free chair conformation. The fundamental understanding of the conformations of cyclohexane and the structures of molecules containing cyclohexane ring was developed by Derek H R Barton and Odd Hassel, who shared the Nobel Prize in 1969. An enormous amount of experimental and theoretical evidence is available on the conformational analysis of these compounds. In this article, distinguishing the conformations of the diastereomers and their relative stabilities are discussed in brief.

Methyl [8-(3,5-di­methyl­pyrazol-1-yl­methyl)-4-methyl-2-oxo-2H-chromen-7-yl­oxy]­acetate 0.19-hydrate

In the title compound, C19H20N2O5·0.19H2O, the coumarin moiety is oriented almost perpendicular to the plane of the pyrazole ring. The crystal structure is stabilized by weak intermolecular C—H⋯π interactions.