SYNTHESIS, CHARACTERIZATION AND CATALYTIC ACTIVITY STUDIES OF OPTICALLY ACTIVE PYRAZOLES

Abstract

The optically active pyrazoles (+)-3(5)(cyclohexylethylamino)methylpyrazole (3c) and (-)-3(5)-N-(phenylmethylene)benzenaminopyrazole (31) were prepared by the reaction of diketopiprazine with optically active amine (+)-cyclohexylethylamine and (- )-N-benzylidenebenzenamine respectively. These compounds (3c) and (39 were characterized by IR, LTV, GC-MS and NMR. After complete characterization these optically active pyrazoles were used to prepare sodium salt in a manner analogous to that of KB(pz)4. Sodium borohydride was heated in presence of 4 equivalent of (3c)/(39 at 220-240 °C until 4 equivalent amount of hydrogen gas was evolved. These tertakis(pyrazolyl)borates {sodiumtetralcisa+)-3(5)cyclohexylethylaminomethylpyrazo -lyllborate (3d) and sodiumtetrakis{(-)-3(5)-N-(Phenylmethylene)benzenamino-pyrazolyllborate (3i)} ligands were used in metal catalyzed enantioselective cyclopropation reaction of styrene with ethyldiazoacetate. The highest enantiomeric exess (ee) obtained was 56% & 65% of compounds (3d) & (3i) respectively for cis isomers and 46% for trans isomers in both compounds. The chemical yield was up to 26-40% & 12-18% for compound (3d) & (3i) respectively.