Raghavakaimal Padmakumar

ZEOLITE MEDIATED MICHAEL ADDITION OF 1,3-DICARBONYL COMPOUNDS AND THIOLS

Abstract Zeolites, an environmentally attractive solid catalyst, proves to be an efficient catalyst for Michael addition of several 1, 3-dicarbonyl compounds and thiols as donors with methyl vinyl ketone, acrolein and methyl acrylate as acceptors without any solvent are described.

Simple, Efficient and Convenient Synthesis of Pyrroles and Pyrazoles Using Zeolites.

Abstract A convenient heterogeneous catalytic methodology for the synthesis of Pyrroles and Pyrazoles by an intermolecular reaction of γ or β-diketones with primary amines or hydrazine derivatives over zeolites are described.

Co-C force constants from resonance Raman spectra of alkylcobalamins: insensitivity to dimethylbenzylimidazole coordination

The Co-C stretching vibration has been identified in resonance Raman spectra of alkyl-cobalamins, via isotope substitution, permitting estimation of the Co-C force constants, f = 1.85, 1.77 and 1.50 mdyn A−1 for methyl-, ethyl- and deoxyadenosyl-cobalamin, respectively (νCo-C = 506, 471 and 442/429 cm−1). These values scale with the reported bond dissociation energies, and support the view that the Co-C bond weakens with increasing bulk of the alkyl group due to steric interaction with the corrin ring. However, the force constants are unaffected by dissociation of the dimethylbenzimidazole ligand at low pH, even though the bond dissociation energy rises significantly upon DMB dissociation in AdoCbl. This increase must therefore reflect destabilization of the CoII product, rather than Co-C bond strengthening in the AdoCbl ground state. The insensitivity of the force constants to dimethylbenzimidazole dissociation implies that the steric effect of DMB coordination is not transmitted to the Co-C bond by the corrin ring. Consistent with this interpretation, the RR frequencies of the corrin ring modes are minimally perturbed by DMB dissociation, supporting earlier NMR results that indicated little change in the corrin conformation.

Zeolite supported permanganate: An efficient catalyst for selective oxidation of enamines, alkylarenes and unsaturated alcohols

Abstract Potassium permanganate supported on zeolite can be used for the selective oxidation of various enamines, alkylarenes and unsaturated alcohols to the corresponding ketones, in good yield. Arenes were selectively oxidized at the benzylic position. If the benzylic carbon is secondary, ketones are obtained, and alcohols are produced if the benzylic position is tertiary. In contrast unsaturated secondary alcohols selectively undergo oxidation to the corresponding olefinic ketones without affecting the carbon-carbon double bonds.

REGIOSELECTIVE REDUCTION OF EPOXIDES AND CONJUGATED CARBONYL COMPOUNDS USING ZEOLITE SUPPORTED ZINC BOROHYDRIDE

Abstract Zeolite supported zinc borohydride is a versatile catalyst for the regeoselective reduction of epoxides, conjugated ketones, and aldehydes to the corresponding alcohols in good yields.

One-pot synthesis of nitroolefins using zeolite

Abstract Nitroolefins, versatile intermediates in organic synthesis, are conveniently prepared in good yields by nitration of olefins using nitric oxide and zeolite as described.

Friedel-Crafts Acylation of Aromatic Hydrocarbons Using Zeolites

Abstract A convenient heterogeneous catalytic methodology for Friedel-Crafts acylation of benzene and toluene using various aliphatic carboxylic anhydrides over zeolites at 250 °C is described. An interesting para selectivity is observed in the case of acylation of toluene over HZSM-5.

Aromatic 3-aza-Cope rearrangement over zeolites

N-Allyl-2-methyl aniline [1a], N-allyl and N-(2′-methyl allyl)-N-methyl anilines [1b & 1 c, respectively] undergo the 3-aza-Cope rearrangement in presence of HY-Zeolite, HEMT and HZeolite beta in hexane at 80°C to give Indoline derivatives as the major product.

Synthesis of Azafluorenones using Zeolites.

Abstract A convenient method for the synthesis of various azafluorenones (2a-f & 4a-d) by cyclization of substituted arylpyridines (1a-f & 3a-d) using zeolites are described.

Diastereoselective Asymmetric Induction in the Thio-Claisen Rearrangement Over Zeolites

Abstract S-Allyl γ-hydroxy ketene dithioacetals [ 1a–1e ] underwent a rapid and diastereoselective thio-Claisen rearrangement into anti α-allyl β-hydroxy dithioesters [ 2a–2e ] over various zeolites at room temperature in hexane is described.