Regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles via three-component coupling of secondary alcohols, TMSN3 and alkynes

1,4-Disubstituted 1,2,3-triazoles are obtained in excellent yields via a three-component coupling of secondary alcohols, alkynes and trimethylsilyl azide (TMSN₃). This one-pot reaction occurs through in situ generation of an azide from the alcohol and TMSN₃, followed by 1,3-dipolar cycloaddition of the terminal alkyne to afford the corresponding disubstituted triazoles.     

A simple and green procedure for the conjugate addition of thiols to conjugated alkenes employing polyethylene glycol (PEG) as an efficient recyclable medium

Polyethylene glycol (PEG) is found to be an inexpensive, nontoxic, environmentally friendly reaction medium for the conjugate addition of thiols to conjugated alkenes to afford the corresponding adducts in excellent yields under mild and neutral conditions. Products of undesirable side reactions resulting from polymerization are not observed. The use of PEG avoids the use of either acid or base catalysts for this conversion and moreover PEG can be recovered and reused.     

Electroorganic synthesis of benzathine

Benzathine is prepared in good yields from cyanobenzene by a combination of electrochemical hydrogenation and Kolbe electrolysis using nickel and platinum electrodes in the presence of methanolic sodium methoxide in an undivided cell.     

Synthesis of thiadiazoles,triazoles and oxadiazoles from sulfonyl acetic acids via a common route

A new class of five membered heterocycles, thiadiazoles, triazoles and oxadiazoles were prepared from sulfonyl acetic acids via acid hydrazides.     

Spectrophotometric determination of dopamine in pharmaceutical formulations

A new spectrophotometric method was developed for the estimation of dopamine. The method is based on the bromination of the dopamine with a solution of excess brominating mixture. After bromination, the excess brominating mixture is treated with potassium iodide to produce a yellow solution. The absorbance of yellow solution was measured at 350 nm on a Spectronic 1001 spectrophotometer against distilled water as a blank.From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 3, 2005, pp. 2842285.Original English Text Copyright © 2005 by Rami Reddy, Sreedevi, Prabhavathi, Chakravarthy.This article was submitted by the authors in English.     

The first example of a liquid crystalline side-chain polymer with bent-core mesogenic units: ferroelectric switching and spontaneous achiral symmetry breaking in an achiral polymer

A dimethylsiloxane diluted polysiloxane side chain co-polymer with non-chiral banana-shaped mesogenic units shows an optically isotropic ferroelectric switching polar smectic C phase (SmCPF) consisting of a conglomerate of homogeneously chiral domains with opposite handedness.     

A one-pot synthesis of 1,4-dithiins and 1,4-benzodithiins from ketones using the recyclable reagent 1,1′-(ethane-1,2-diyl)dipyridinium bistribromide (EDPBT)

A novel access to 1,4-dithiins and 1,4-benzodithiins from the corresponding ketones in one-pot using the recyclable reagent, 1,1′-(ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) is described. This method is mild, simple, environmentally benign and is applied successfully for the ring expansion of 1,3-dithiolane to 1,4-dithiins and the ring expansion associated with aromatisation of cyclic ketones with or without double bonds in the ring. The main feature of this method is that EDPBT acts as a promoter in the formation of 1,3-dithiolane and as a reagent in the ring expansion step. The spent reagent can be recovered, regenerated and reused.     

Enzymatic kinetic resolution of racemic 4-tetrahydropyranols by Candida rugosa lipase

Enzymatic kinetic resolution of (±)-hydroxytetrahydropyrans has been achieved for the first time by means of lipase-mediated transesterification to afford optically active (2S,4R)-tetrahydropyranyl acetates and (2R,4S)-tetrahydropyranols in excellent yields with high enantioselectivity. Absolute configurations of the tetrahydropyranyl acetates were assigned as (S) by chemical correlation.     

A mild, rapid and highly regioselective ring-opening of epoxides and aziridines with acetic anhydride under solvent-free conditions using ammonium-12-molybdophosphate

A highly regioselective ring opening of epoxides and aziridines can be carried out efficiently with acetic anhydride to form the acetates of the corresponding 1,2-diols and 2-amino-alcohols, respectively, using ammonium-12-molybdophosphate (AMP) as a heterogeneous catalyst, at room temperature, in the absence of solvent.     

Sensitive and selective spectrophotometric method for the determination of trace amounts of osmium with 1,2,3-indanetrione monothiosemicarbazone

Summary Sensitive and Selective Spectrophotometric Method for the Determination of Trace Amounts of Osmium with 1,2,3-Indanetrione Monothiosemicarbazone A simple, sensitive and selective spectrophotometric method has been developed for the determination of osmium using 1,2,3-indane-trione monothiosemicarbazone (ITMT). The method is based on the colour reaction between ITMT and osmium(VIII) in hydrochloric acid (0.32–0.60 M) medium. The calibration graph for measurement at 440 nm is linear in the range 1.4–33.6g of osmium per 25ml, with a molar absorptivity of 6.43×10⁴l·mole^–1·cm^–1. The effect of interferences has been studied and the method applied to the determination of osmium in synthetic samples whose composition correspond to osmiridium or syserkite, with good results.