Pradip Kumar Tapaswi

Water-Mediated Synthesis of 2-Substituted Benzimidazoles by Boric Acid and Glycerol

A very simple, mild, and highly efficient green catalyst has been developed for the synthesis of 2-substituted benzimidazoles by treatment of substituted ortho-phenylenediamines and aldehydes in water at 80°C in the presence of boric acid (5 mol-%) and glycerol (0.05 mL). This methodology has been standardized on 55 substrates, and nine new compounds have been synthesized.

Highly Efficient and Simple Catalytic System for the N-Arylation of Some Hindered Aza-Heterocycles in Water

Abstract A highly efficient and simple protocol for the N-arylation of some hindered aza-heterocycles in water has been developed with readily available basic copper carbonate as the catalyst using bis(3,5-dimethyl-1H-pyrazol-1-yl)methane as ligand. This mild catalytic system possesses excellent tolerance for a large variety of functional groups. A total of 11 previously unknown coupling products have been synthesized by this methodology. GRAPHICAL ABSTRACT

A facile and efficient synthesis of tri- and tetrasubstituted imidazoles with potassium hydrogen sulfate and DB18C6 in an aqueous medium

Abstract Potassium hydrogen sulfate in the presence of dibenzo-18-crown-6 (DB18C6) turns out to be a very efficient and effective catalyst for the facile synthesis of a wide variety of tri- and tetrasubstituted imidazoles in an aqueous medium at moderate temperature. The idea behind this is that the potassium ion, being trapped in the crown core, frees the hydrogen sulfate anion, which, because of its acidic nature, succeeds in the ready synthesis of the imidazoles.

Halogen-Free Room-Temperature Brønsted Acidic Ionic Liquid [Hmim]+ HSO4 − as a Recyclable Green “Dual Reagent” Catalysis for the Synthesis of Triarylmethanes (TRAMs)

Abstract The halogen-free Brønsted acidic ionic liquid methylimidazolium hydrogen sulfate ([Hmim]+ HSO4 −) acts as a very efficient catalyst for the one-pot, two-component Baeyer condensation of a variety of aromatic aldehydes with dimethyl or diethyl aniline at room temperature. This “green” reagent behaves as both catalyst and solvent; that is, it exhibits “dual-reagent catalysis.” The room-temperature acidic ionic liquid could be recycled several times with almost no loss in the yield of the reaction. This is the first report of the Baeyer synthesis with a halogen-free ionic liquid. GRAPHICAL ABSTRACT

Charge transfer energies of the complexes of (dibenzoylmethanato)boron difluoride with indeno-pyridines and polynuclear aromatic hydrocarbons

Charge transfer complexes of electron deficient (dibenzoylmethanato)boron difluoride (DBMBF2) with polyaromatic hydrocarbons (A), as well as with highly electron rich indeno-pyridines (I) compounds in ethanol medium have been studied by electronic absorption spectroscopy. Absorption band due to a charge-transfer (CT) transitions are observed in the visible region. Utilizing the CT transition energy, the vertical electron affinities (EA(v)) of DBMBF2 in ethanol has been calculated. The value of EA(v) for DBMBF2 is found to be 2.28 eV, this is the first report of its electron affinity value. We have calculated the degrees of CT and transition dipole strengths of the DBMBF2/A and DBMBF2/I complexes. Along with both theoretically calculated and experimentally obtained vertical ionization potentials of the indeno-pyridine donors have been estimated for the first time. I show high degree of charge transfer along with high ground state stability similar to that of A. Thus indeno-pyridine (I) donors are also as good as aromatic hydrocarbons (A) for DBMBF2, having equivalent ionization potential like that of aromatic hydrocarbons.