A stereoselective method for the synthesis of substituted tetrahydrofuran derivatives employing a tandem alkylation-Michael addition sequence to vinylogous carbonates is developed. The method could be used to synthesize THFs bearing tertiary ethers. Further, the method is extended to the synthesis of adjacent bis-THFs. 相似文献
1,3-Diaryl propargyl alcohols undergo smooth intramolecular Friedel-Crafts cyclization with triethylsilane in the presence of 10 mol % iodine 3-aryl-1H-indene derivatives in good yields in short reaction times. This is the first example on the synthesis of substituted indenes from 1,3-diaryl propargyl alcohols. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient, and practical. 相似文献
Three-component coupling (3CC) of kojic acid, aldehyde and 1,3-dione has been achieved in the presence of 10 mol % InCl3 under solvent-free conditions to afford the corresponding dihydropyrano[3,2-b]chromenedione derivatives in good yields. This is the first example of the condensation of kojic acid, aldehyde and 1,3-diones to provide a novel series of kojic acid derivatives. 相似文献
<正>A series of some new 2-imino-5-[(Z)-1-(4-methylphenyl)methylidene]-3-[5-(2-oxo-2H-3-chromenyl)-1,3-oxazol-2-yl]-1,3- thiazolan-4-ones 5a-j has been synthesized and assayed for their antibacterial activity against Gram-positive bacteria viz.Bacillus subtilis(ATCC 6633),Staphylococcus aureus(ATCC 6538p) and Micrococcus luteus(IFC 12708),and Gram-negative bacteria viz. Proteus vulgaris(ATCC 3851).Salmonella typhimurium(ATCC 14028) and Escherichia coli(ATCC 25922).Among the screened compounds,5d,5e,5f,5g,and 5j exhibited potent inhibitory activity compared to standard drug,and emerged as potential molecules for further development. 相似文献
Novel, economic and environmentally friendly one-pot three-component Knoevenagel/hydrogenation (K/H) and four-component Knoevenagel/hydrogenation/alkylation (K/H/A) reactions of ketones, CH-acids, dihydropyridines and alkyl halides using proline and proline/metal carbonate catalysis, respectively, have been developed. Many of the products of these K/H and K/H/A reactions have direct applications in pharmaceutical chemistry. 相似文献
A highly chemoselective conjugate reduction of electron-deficient Michael acceptors, including alpha,beta-unsaturated ketones, carboxylic esters, nitriles and nitro compounds with PMHS in the presence of catalytic B(C6F5)3 is described. 相似文献
A rapid and sensitive substoichiometric radiochemical procedure has been developed for the extraction of cobalt with potassium
salts of ethyl, propyl, butyl, pentyl and benzyl xanthates. The relative extractabilities of the cobalt-xanthate complexes
into chloroform and carbon tetrachloride were studied. Substoichiometric quantification methods were developed in each case
and utilised to determine the cobalt content present in standard solutions as well as biological samples. 相似文献
Near-infrared (NIR) and IR spectroscopy have been applied for the characterisation of three complex Cu–Zn sulphate/phosphate
minerals, namely ktenasite, orthoserpierite and kipushite. The spectral signatures of the three minerals are quite distinct
in relation to their composition and structure. The effect of structural cation substitution (Zn2+ and Cu2+) on band shifts is significant both in the electronic and in the vibrational spectra of these Cu–Zn minerals. The variable
Cu:Zn ratio between Zn-rich and Cu-rich compositions shows a strong effect on Cu(II) bands in the electronic spectra. The
Cu(II) spectrum is most significant in kipushite (Cu-rich) with bands displayed at high wavenumbers, 11,390 and 7,545 cm−1. The isomorphic substitution of Cu2+ for Zn2+ is reflected in the NIR and IR spectroscopic signatures. The multiple bands for ν3 and ν4 (SO4)2− stretching vibrations in ktenasite and orthoserpierite are attributed to the reduction in symmetry of the sulphate ion from
Td to C2V. The IR spectrum of kipushite is characterised by strong (PO4)3− vibrational modes at 1,090 and 990 cm−1. The range of IR absorption is higher in ktenasite than in kipushite, while it is intermediate in orthoserpierite. 相似文献
Formaldehyde has been highlighted as potential genotoxic impurity (GTI). Trace-level quantification of GTIs in drug substances requires sensitive, precise and accurate analytical methodologies for their estimation in drug substances and control. Analysis and estimation of formaldehyde is very challenging due to its properties namely volatility, high polarity, low molecular weight and over and above the absence of chromophore. This article presents a validated HPLC–UV method which is sensitive to quantification of formaldehyde in active pharmaceutical ingredient. As formaldehyde does not possess chromophore, the developed HPLC method involves derivatization with 2,4-dinitrophenylhydrazine. Using this method, the detection and quantitation limits achieved are 0.5 and 1.5 ppm, respectively. The calibration curve of formaldehyde was linear over the concentration range of 1.5–20 ppm. The method was found to be sensitive, precise and accurate and the proposed method has been successfully applied to estimate formaldehyde content in scale-up batches of bulk drug.