Novel synthesis of 2-arylbenzothiazoles mediated by ceric ammonium nitrate (CAN)

[reaction: see text] Cyclization of the intermediate radical formed after initial oxidative coupling between thiophenols and aromatic nitriles leads to the synthesis of a wide range of 2-arylbenzothiazoles.     

Study of heterogeneous interaction in binary mixtures of 2-methoxyethanol-water using dielectric relaxation spectroscopy

The dielectric relaxation measurements on binary mixtures of 2-methoxyethanol with water have been carried out over entire concentrations and at temperature range of 0 °C to 25 °C using a picosecond time domain reflectometry technique. The complex dielectric permittivity spectra of 2-methoxyethanol/water mixtures were fitted using Havriliak-Negami equation. The static dielectric constant and relaxation time for all concentrations were obtained using least square fit method. The principal relaxation time is small if compared to that of corresponding alcohol/water mixtures this may be due to the hydrogen bonding ether oxygen in the 2-ME-water system. Excess dielectric properties, Kirkwood correlation factor, thermodynamic properties and Bruggeman factor are also determined and the results are interpreted in terms of heterogeneous interactions among the unlike molecules due to hydrogen bonding.     

Chemoselective Protection of Hydroxyl Groups and Deprotection of Silyl Ethers

Summary.  Trimethylsilylation of alcohols and phenols is carried out using hexamethyldisilazane and LiClO₄ under microwave irradiation and neutral conditions. The deprotection of silyl ethers is carried out similarly using natural kaolinitic clay and a few drops of water. Received March 1, 2001. Accepted (revised) April 17, 2001     

Microwave Induced Synthesis of Geminal Diacetates from Aldehydes Using Envirocat EPZ10® Without Solvent

Summary.  A simple, efficient, and environmentally friendly synthesis of geminal diacetates using Envirocat EPZ10^? under microwave activation and solvent-free conditions is described. Easy separation and recyclability of the catalyst, high reaction rates, high yields, and easy work-up are important advantages of this method. Received November 3, 1999. Accepted November 24, 1999     

The dielectric relaxation study of 2(2-alkoxyethoxy)ethanol-water mixtures using time domain reflectometry

Complex permittivity spectra of 2(2-alkoxyethoxy)ethanol-water mixtures for the entire concentration range and at 25 °C have been measured using time domain reflectometry technique up to 30 GHz. The relaxation processes have been obtained by fitting the complex permittivity spectra of the binary mixtures in 2-Debye equation. In glycol ether-water mixtures except for pure water and its rich region the double relaxation times, primary process (τ₁) and secondary process (τ₂) have been observed. The primary relaxation process (τ₁) may be due to cooperative relaxation of the H-bond network of mixture constituents and the secondary relaxation process (τ₂) may be due to its flexible parts attached to the carbon chain. The intra and intermolecular hydrogen bonding of 2(2-alkoxyethoxy)ethanol in pure form as well as in binary mixtures of water have been discussed using Kirkwood correlation factor, Excess dielectric properties and the Bruggeman factor.     

Facile Tetrahydropyranylation of Alcohols and Phenols Using Anhydrous Calcium Chloride under Mild and Neutral Conditions

Summary.  Treatment of 3,4-dihydro-2H-pyran with various alcohols and phenols in the presence of a catalytic amount of anhydrous calcium chloride in dichloromethane furnished tetrahydropyranyl ethers under almost neutral conditions. Corresponding author. E-mail: bandgar_bp@yahoo.com Received January 25, 2002; accepted (revised) March 20, 2002