Suresh B. Waghmode

Liquid phase oxidation of amines to azoxy compounds over ETS-10 molecular sieves

A convenient method for the oxidation of aryl amines to azoxybenzenes with H2O2 or tertiary butyl hydroperoxide over the titanosilicate ETS-10 is reported. Over ETS-10, aniline is transformed into azoxybenzene in greater than 97% yield with H2O2 as the oxidant. Substituted anilines are also transformed in good yields. Yield and H2O2 efficiency depend largely on experimental parameters such as catalyst concentration, H2O2: substrate mole ratio and the nature of the solvent.

Organocatalytic Approach to (S)-1-Arylpropan-2-ols: Enantioselective Synthesis of the Key Intermediate of Antiepileptic Agent (−)-Talampanel

An efficient organocatalytic route for the preparation of enantioselective synthesis of (S)-1-arylpropan-2-ols derivatives, including the key intermediate of antiepileptic agent (−)-talampanel is described. The key steps involved are L-proline-catalyzed asymmetric α-aminooxylation of aldehydes and regioselective tosylation of diols followed by reduction.

Efficient liquid phase acylation of alcohols over basic ETS-10 molecular sieves

Abstract Acylation of alcohols with acetic acid can be carried out efficiently in the liquid phase over microporous titanosilicate ETS-10-type catalysts. The reaction was studied over ETS-10 exchanged with, Li, Na, K, Rb, Cs, Ba and H ions. Activity for acylation of primary alcohols depends on the exchanged alkali ion and increases in the order Li

Efficient Method for Demethylation of Aryl Methyl Ether Using Aliquat-336

Abstract A rapid method for selective cleavage of aryl methylethers can be achieved in the presence of a protic acid and a catalytic amount of phase-transfer catalyst (Aliquat-336). Aliquat-336 accelerates the rate of reaction and affords the corresponding phenols in excellent to good yields on a wide variety of substrates. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Facile preparation of tetrahydro-5H-pyrido[1,2,3-de]-1,4-benzoxazines via reductive cyclization of 2-(8-quinolinyloxy)ethanones and their antioxidant activity.

Pd/C-catalyzed reductive cyclization of 1-aryl-2-(8-quinolinyloxy)ethanones opens a facile access to the title compounds in good yields. The scope of this reductive cyclization is explored and the antioxidant activities of the products are studied.

Heterogeneous photocatalysed Heck reaction over PdCl2/TiO2

The heterogeneous PdCl2/TiO2 efficiently catalyzes the C–C bond formation (Heck reaction) between aryliodides and olefins under photochemical and mild reaction conditions. This process gives good to excellent conversion under optimized reaction conditions. After completion of the reaction, Pd2+ is reduced to Pd0. Further, Pd0 can be easily converted into Pd2+ by heating with ammonium chloride at 400 °C for 30 min and the regenerated catalyst could be reused up to the third recycle with good catalytic activity. The catalysts (before and after reaction, as well as regenerated) were systematically characterized using Transmission Electron Microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, temperature programmed reduction and DRUV-visible spectroscopy techniques.

Photodissociation dynamics of 3-bromo-1,1,1-trifluoro-2-propanol and 2-(bromomethyl) hexafluoro-2-propanol at 234 nm: Resonance-enhanced multiphoton ionization detection of Br (2Pj)

The photodissociation dynamics of 3-bromo-1,1,1-trifluoro-2-propanol (BTFP) and 2-(bromomethyl) hexafluoro-2-propanol (BMHFP) have been studied at 234 nm, and the C-Br bond dissociation investigated using resonance-enhanced multiphoton ionization coupled with time-of-flight mass spectrometer (REMPI-TOFMS). Br formation is a primary process and occurs on a repulsive surface involving the C-Br bond of BTFP and BMHFP. Polarization dependent time-of-flight profiles were measured, and the translational energy distributions and recoil anisotropy parameters extracted using forward convolution fits. A strong polarization dependence of time-of-flight profiles suggest anisotropic distributions of the Br((2)P(3/2)) and Br((2)P(1/2)) fragments with anisotropy parameter, β, of respectively 0.5 ± 0.2 and 1.2 ± 0.2 for BTFP, and 0.4 ± 0.1 and 1.0 ± 0.3 for BMHFP. The measured velocity distributions consist of a single velocity component. The average translational energies for the Br((2)P(3/2)) and Br((2)P(1/2)) channels are 9.2 ± 1.0 and 7.4 ± 0.9 kcal/mol for BTFP, and 15.4 ± 1.8 and 15.1 ± 2.0 kcal/mol for BMHFP. The relative quantum yields of Br((2)P(3/2)) and Br((2)P(1/2)), which are 0.70 ± 0.14 and 0.30 ± 0.06 in BTFP and 0.81 ± 0.16 and 0.19 ± 0.04 in BMHFP, indicate that the yield of the former is predominant. The measured anisotropy parameters for the Br((2)P(3/2)) and Br((2)P(1/2)) channels suggest that the former channel has almost equal contributions from both the parallel and the perpendicular transitions, whereas the latter channel has a significant contribution from a parallel transition. Non-adiabatic curve crossing plays an important role in the C-Br bond dissociation of both BTFP and BMHFP. The estimated curve crossing probabilities suggest a greater value in BTFP, which explains a greater observed value of the relative quantum yield of Br((2)P(1/2)) in this case.

Synthesis of N-Boc-C1 Vinyl Tetrahydroisoquinoline via Zn-Mediated Intramolecular Cyclization of N-Boc Protected Iodo Acetonide

Abstract The Zn-mediated elimination of N-Boc protected iodo acetonide undergoes intramolecular cyclization to afford N-Boc-C1 vinyl tetrahydroisoquinoline in good yield.

Molecular modeling studies on zeolite catalysts for shape-selective electrophilic substitution: formation of xylenes

Energy minimization methodology has been used to study the interaction of isomers of xylene with ZSM-5, mordenite and MCM-22 zeolites. Adsorption sites and the mechanism of diffusion of the reactant molecules in the alkylation of toluene and xylene isomers inside these zeolites were studied. When molecules diffuse through 10-member and 12-member ring channels, they pass through favorable and unfavorable adsorption sites. ZSM-5 shows significant selectivity for p-xylene over the o- and m-xylenes. In large pore mordenite, the difference between favorable and unfavorable adsorption sites is not significant for xylene isomers. In the case of MCM-22, there are significant energy barriers, and the diffusivity is not high in spite of the presence of large cages. Results of this study emphasize the importance of the shape and the size of molecules as well as the pore dimensions and architecture of zeolites in effectively controlling molecular diffusion characteristics. The diffusion characteristics of the molecules inside a zeolite are sensitive to its pore architecture. The results offer the reasons based on molecular level interactions, for the experimentally observed shape selectivities in the above three zeolites.

Photodissociation of 3-bromo-1,1,1-trifluoro-2-propanol at 193 nm: laser-induced fluorescence detection of OH(nu'' = 0, J'').

Photodissociation of 3-bromo-1,1,1-trifluoro-2-propanol (BTFP) has been investigated at 193 nm, employing the laser photolysis laser-induced fluorescence technique. The nascent OH product was detected state selectively, and the energy released into translation, rotation, and vibration of the photoproducts has been measured. OH is produced mostly vibrationally cold, with a moderate rotational excitation, which is characterized by a rotational temperature of 640 +/- 140 K. However, an appreciable amount of the available energy of 36.1 kcal mol(-1) is released into translation of OH (15.1 kcal mol(-1)). OH product has no preference for a specific spin-orbit state, Pi(3/2) or Pi(1/2). However, between two Lambda-doublet states, Pi(+) and Pi(-), the OH product has a preference for the former by a factor of 2. A mechanism of OH formation from BTFP on excitation at 193 nm is proposed, which involves first the direct C-Br bond dissociation from a repulsive state (n(Br)sigma*(C-Br)) as a primary process. The primary product, F(3)C-CH(OH)-CH(2), with sufficient internal energy undergoes spontaneous C-OH bond dissociation, through a loose transition state. The formation rate of OH is calculated to be 5.8 x 10(6) s(-1) using Rice-Ramsperger-Kassel-Marcus unimolecular rate theory. Experimental results have been supported by theoretical calculations, and energies of various low-energy dissociation channels of the primary product, F(3)C-CH(OH)-CH(2), have been calculated.