The reductive etherification of carbonyl compounds using polymethylhydrosiloxane activated by molecular iodine

Aldehydes and ketones undergo a smooth reductive etherification by polymethylhydrosiloxane (PMHS) in the presence of a catalytic amount of molecular iodine under mild conditions to afford the corresponding symmetrical ethers in excellent yields. This new reagent system (PMHS/I₂) provides a simple and convenient route for the preparation of symmetrical ethers from carbonyl compounds.     

Tandem SN2-Michael addition to vinylogous carbonates for the stereoselective construction of 2,3,3,5-tetrasubstituted tetrahydrofurans

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.     

Iodine/Et3SiH: a novel reagent system for the synthesis of 3-aryl-1H-indenes from 1,3-diaryl propargyl alcohols

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.     

InCl3-catalyzed three-component reaction: a novel synthesis of dihydropyrano[3,2-b]chromenediones under solvent-free conditions

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.     

Synthesis of some new 3-[5-(2-oxo-2H-3-chromenyl)-1,3-oxazol-2-yl]-1,3-thiazolan-4-ones as antimicrobials

<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.     

Development of drug intermediates by using direct organocatalytic multi-component reactions

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.     

A facile and chemoselective conjugate reduction using polymethylhydrosiloxane (PMHS) and catalytic B(C6F5)3

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.     

Substoichiometric extraction and quantification of cobalt with potassium salts of ethyl, propyl, butyl, pentyl and benzyl xanthates

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.     

Spectroscopy of selected copper group minerals: ktenasite,orthoserpierite and kipushite

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 T_d to C_2V. 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.