Kumar K. Mahalanabis

Spectroscopic investigation of 3-pyrazolyl 2-pyrazoline derivative in homogeneous solvents.

How solvent conditions such as solvent polarity and hydrogen-bonding affect the fluorescence of a newly synthesized 3-pyrazolyl 2-pyrazoline derivative (Pyz) having pharmaceutical activity has been explored. The solvatochromic effect of Pyz is due to a change in dipole moment of the compound in the excited state. The relaxation of S1 state is perturbed in hydrogen-bonding solvents. The fluorescence properties of the systems are strongly dependent on the polarity of the media. The non-radiative relaxation process is facilitated by an increase in the polarity of the media. The photophysical response of Pyz in different solvents has been explained considering solute-solvent interactions.

Application of least squares method in matrix form: simultaneous determination of ibuprofen and paracetamol in tablets

Least squares method in matrix form which is K-matrix representation of Beers law is presented for simultaneous determination of ibuprofen and paracetamol in tablets without prior separation from each other. The concentration of each component in the mixture was determined spectrophotometrically from absorbances of the mixture measured at 225, 226, 228, 232, 230, 234, and 235 nm. Mixtures of known composition were used as standards to minimise errors due to presence of both compounds in the same solution. Excellent results were obtained by this method.

Simultaneous spectrophotometric determination of metronidazole and furazolidone with multistandard addition and a least-squares method

Abstract A least-squares method in matrix form (the ϰ-matrix form of Beers law) is presented for the simultaneous determination of metronidazole and furazolidone in tablets. The concentration of each compound was determined from the absorbances measured in the range 305–350 nm at 5-nm intervals. Mixtures of known composition were used as standards to minimize errors arising from the presence of both compounds in the same solution. The results obtained were accurate and precise.

PREPARATION OF 4-CYANO-3-METHYL-1-PHENYL-1H-PYRAZOLE-5-(4-BROMOPHENYL)-NITRILE IMINE : REGIO-AND STEREOSELECTIVE SYNTHESIS OF A NEW CLASS OF SUBSTITUTED 3-PYRAZOLYL-2-PYRAZOLINES AND PYRAZOLES

A regio and stereoselective preparation of a new class of substituted 3-pyrazolyl-2-pyrazolines and pyrazoles in good to excellent yields has been developed by reacting 4-cyanopyrazole-5-nitrile imine with dipolarophiles.

Application of the least-squares method in the matrix form: simultaneous spectrophotometric determination of rifampicin and isoniazid in binary pharmaceutical formulations

A least-squares method in the matrix form is described for the simultaneous determination of rifampicin and isoniazid in a mixture. The method allows the rapid analysis of binary pharmaceutical formulations with minimum error. The concentration of each component in the mixture has been determined spectrophotometrically by measuring the absorbance of the mixture at 5-nm intervals from 230 to 290 nm. To calculate the matrix of the proportionality constant a standard mixture was used for each component. All data analyses were performed on a personal computer.

Studies on β-Enaminonitriles: A one-pot Regiospecific Synthesis of Polysubstituted 3,4-Dihydro-2(1H)-Pyridones

Abstract Reaction of α, β-unsaturated acid chlorides with primary enaminonitriles in presence of triethylamine affords, under very mild conditions, a simple and highly efficient regiospecific synthesis of polysubstituted 3,4-dihydro-2(1H)-pyridones.

Synthesis of Novel 3,5‐Disubstituted‐4‐isothiazolecarbonitriles

Abstract α‐Cyano‐β‐enaminones, obtained by regioselective acylation of β‐enaminonitriles, were smoothly converted to thiones which on oxidative cyclization afforded 3,5‐disubstituted‐4‐isothiazolecarbonitriles in good to excellent yields.

A short and expeditious regiospecific synthesis of novel pyrazoles

α-Cyano-β-enaminones, obtained by regioselective acylation of β-aminocrotononitrile, are smoothly and regiospecifically converted into substituted pyrazoles in good to excellent yields.

Synthesis of substituted isoxazolones and isoxazoles from cyanoenaminones

α-Cyano-β-enaminones, obtained by regioselective acylation of β-aminocrotononitrile, are smoothly and regiospecifically converted into substituted 5-isoxazolones, which on alkaline hydrolysis afford 4-acyl-3-substituted-5-hydroxyisoxazoles in good to excellent yields.

The synthesis of novel ethyl 4-(substituted amino)isothiazolo[5,4-b]-pyridine-5-carboxylates

The preparation of ethyl 4-(substituted amino)isothiazolo[5,4-b]pyridine-5-carboxylates via nucleophilic displacement of 4-chloroisothiazolo[5,4-b]pyridines by amino compounds is reported.