Differentiation of isomeric 2-aryldimethyltetrahydro-5-quinolinones by electron ionization and electrospray ionization mass spectrometry

A series of isomeric 2-aryl-6,6-dimethyltetrahydro-5-quinolinones (set I) and 2-aryl-7,7-dimethyltetrahydro-5-quinolinones (set II) were studied under positive ion electron ionization (EI) and electrospray ionization (ESI) techniques. Under EI conditions, the molecular ions were found to be less stable in set I isomers, and they resulted in abundant fragment ions, i.e., [M-CH(3)](+), [M-CO](+.), [M-HCO](+), [M-(CH(3),CO)](+), and [M-(CH(3),CH(2)O)](+), when compared with set II isomers. In addition, the set I isomers showed specific fragment ions corresponding to [M-OH](+) and [M-OCH(3)](+). The retro-Diels-Alder (RDA) product ion was always higher in set II isomers. The ESI mass spectra produced [M + H](+) ions, and their decomposition showed favorable loss of CH(3) radical, CH(4) and C(2)H(6) molecules in set I isomers. The set II isomers, however, showed predominant RDA product ions, and specific loss of H(2)O. The selectivity in EI and ESI was attributed to the instability of set I isomers by the presence of a gem-dimethyl group at the α-position, and it was supported by the data from model compounds without a gem-dimethyl group. Density functional theory (DFT) calculations successfully corroborated the fragmentation pathways for diagnostic ions. This study revealed the effect of a gem-dimethyl group located at the α-position to the carbonyl having aromatic/unsaturated carbon on the other side of the carbonyl group.     

Unique copper–salen complex: an efficient catalyst for N-arylations of anilines and imidazoles at room temperature

We have reported here the catalytic activity of a unique Cu–salen type complex in N-arylation of anilines with arylboronic acids in water. The protocol is found to be applicable for a wide range of electronically diversified arylboronic acids and anilines with excellent yields of the isolated product. Further the scope of this protocol has been extended to the synthesis of various N-aryl imidazoles in iso-propanol.     

A Rapid HPTLC Method for Standardization of Ficus bengalensis Linn.

JPC – Journal of Planar Chromatography – Modern TLC - Because of the increasing importance of Ficus bengalensis as a potent antidiabetic herbal drug, detailed chemical and analytical...     

Synthesis of Biaryl Derivatives of Spirofurochromanone in Water and Their Anticancer Activity

Russian Journal of General Chemistry - Biaryl derivatives of spirofurochromanones have been synthesised from 4-bromophenyl derivatives of spirofurochromanones upon catalysis by Pd/C in water....     

Computations of a laminar backward‐facing step flow at Re=800 with a spectral domain decomposition method

The two‐dimensional laminar incompressible flow over a backward‐facing step is computed using a spectral domain decomposition approach. A minimum number of subdomains (two) is used; high resolution being achieved by increasing the order of the basis Chebyshev polynomial. Results for the case of a Reynolds number of 800 are presented and compared in detail with benchmark computations. Stable accurate steady flow solutions were obtained using substantially fewer nodes than in previously reported simulations. In addition, the problem of outflow boundary conditions was examined on a shortened domain. Because of their more global nature, spectral methods are particularly sensitive to imposed boundary conditions, which may be exploited in examining the effect of artificial (non‐physical) outflow boundary conditions. Two widely used set of conditions were tested: pseudo stress‐free conditions and zero normal gradient conditions. Contrary to previous results using the finite volume approach, the latter is found to yield a qualitatively erroneous yet stable flow‐field. Copyright © 1999 John Wiley & Sons, Ltd.     

Gold(I)-catalyzed unprecedented rearrangement reaction between 2-aminobenzaldehydes with propargyl amines: an expedient route to 3-aminoquinolines

Access to aminoquinolines: a gold(I)-catalyzed unprecedented rearrangement reaction between 2-aminobenzaldehydes with propargyl amine was studied. The study provided, for the first time, direct access to 3-aminoquinolines in one step starting from readily available starting materials. Elegantly designed experiments were employed to unravel the mechanism of this unprecedented rearrangement, which are corroborated by DFT calculations.     

Computer simulation of molecular organization in a nematogen. The role of thermodynamic parameters

Computer simulations of molecular organization in a nematogen, alkenyl bicyclohexylnitrile (ALBCHNL), have been carried out with respect to translational and orientational motions. The atomic net charge and dipole moment at each atomic center has been evaluated using the complete neglect of differential overlap (CNDO/2) method. The modified Rayleigh-Schroedinger perturbation theory, along with multicentered-multipole expansion method, has been employed to evaluate long-range intermolecular interactions, while a “6-exp” potential function has been assumed for short-range interactions. The total interaction energy values obtained through these computations have been used as input to calculate the thermodynamical parameters such as entropy and Helmholtz free energy of each configuration at room temperature (300 K), nematic-isotropic transition (364.7 K) and above transition temperature (450 K). An attempt has been made to understand the molecular organization, to develop a new and interesting model for nematogen based on the thermodynamic parameters introduced in this article.     

An efficient and reusable vanadium based catalytic system for room temperature oxidation of alcohols to aldehydes and ketones

A simple and efficient vanadium based catalyst system for the oxidation of primary and secondary alcohols to aldehydes or ketones is reported using tert-butyl hydroperoxide as oxidizing agent and vanadyl sulfate as catalyst at room temperature. The versatility of the catalytic protocol is studied with wide variety of substrates.