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991.
The direct 3-arylthiolation of indoles with aromatic thiols has been achieved in the presence of Selectfluor™ under mild conditions to produce 3-arylthioindoles in relatively good to excellent yields and with high selectivity. This method is effective even with 2-unsubstituted indoles. 相似文献
992.
Kesava Reddy M Vijaya Bhaskar Reddy M Jayakrishna G Gunasekar D Caux C Bodo B 《Chemical & pharmaceutical bulletin》2003,51(2):191-193
Two new flavonoids, 5, 7, 2', 5'-tetramethoxyflavanone (1) and 5-hydroxy-7, 2'-dimethoxyflavone (2), together with two known flavones, skullcapflavone I (3) and echioidin (4) were isolated from the whole plant of Andrographis rothii. The structures of the new compounds were established by extensive one- and two-dimensional (1D- and 2D-) NMR spectral studies. 相似文献
993.
Oxiranes undergo ring opening rapidly with sodium azide in a [bmim]BF4/H2O or [bmim]PF6/H2O (2:1) solvent system, under mild and neutral reaction conditions to afford the corresponding 2-azidoalcohols in high to quantitative yields. The remarkable features of this procedure are improved yields, enhanced reaction rates, high regioselectivity and ease of recyclability of ionic liquids (ILs). The recovered ionic liquid can be reused for four to five times but with gradual decrease in activity. 相似文献
994.
P. Vijay Kumar Reddy P. Naveen Kumar G. V. P. Chandramouli 《Journal of heterocyclic chemistry》2005,42(2):283-286
A variety of novel 6,6′‐arylidene‐bis‐[5‐hydroxy‐9‐methyl‐2,3‐diaryl‐thieno[3,2‐g]thiocoumarins] 3a‐d , 4a‐d , 5a‐d , and 6a‐d were obtained by a reaction between 5‐hydroxy‐9‐methyl‐2,3‐diarylthieno[3,2‐g]thiocoumarins 1a‐d with aromatic aldehydes 2a‐d in isopropyl alcohol. The synthesized compounds were tested for their antimicrobial activity. 相似文献
995.
A novel and general method has been developed for the stereoselective construction of 5-hydroxymethyl azabicyclic ring skeletons based on epoxide-initiated cationic cyclization of azides. The key cyclization reaction was systematically studied with the model compound, 3-(1-oxa-spiro[2.4]hept-4-yl)propyl azide 3a, and EtAlCl(2) was found to be an ideal choice as the catalyst. The generality of this transformation was further tested with different ring sizes, where six- and seven-membered epoxyazides 3b,c underwent smooth cyclization to give 5-hydroxymethyl azepine 4b and 5-hydroxymethyl azocine 4c, respectively, as a single detectable diastereomer. This novel methodology was elegantly applied in the stereoselective total synthesis of indolizidine alkaloids 167B and 209D. Further, the enantioselective total synthesis of natural and unnatural indolizidine alkaloids 167B and 209D was accomplished by using Sharpless asymmetric dihydroxylation as a key step. 相似文献
996.
The extraction of cobalt/II/ from ammonium thiocyanate solutions by di-n-pentyl sulphoxide /DPSO/, di-n-octyl sulphoxide /DOSO/ and their mixtures in carbon tetrachloride has been studied. The species extracted were found to be Co/SCN/2. 4S /where S=DOSO or DOSO/. Synergic effects have been observed which are ascribed to the formation of mixed ligand metal complexes. The influence of the metal concentration, temperature and the diluent on the extraction of cobalt/II/has been investigated. 相似文献
997.
Benjaram M. Reddy G. Sarala Devi Pavani M. Sreekanth 《Research on Chemical Intermediates》2002,28(6):595-601
The vapor-phase catalytic O-alkylation of - and -naphthols with methanol has been investigated over lanthanum, cerium, samarium, and antimony phosphate catalysts promoted with cesium hydroxide. Among various catalysts investigated, the Cs-SmPO4 combination catalyst provided better catalytic activity and selectivity. The CsOH promoter suppressed formation of C-alkylated side products and enhanced the O-alkylation selectivity. Characterization of these catalysts by X-ray diffraction and FT-infrared techniques revealed that the cesium promoter has no influence on the bulk structure of the catalysts. Temperature programmed desorption of anhydrous ammonia over promoted and unpromoted catalysts revealed that the cesium promoter decreases total surface acidity of the catalysts. 相似文献
998.
Substituent effects on 199Hg1H and 199Hg13C spinspin coupling constants have been studied for neopentylmercury derivatives, (CH3)3CCH2HgR(or X), where R is covalently bonded Me, Et, t-Bu, neopentyl, and vinyl, and X is easily ionizable CN, Br, Cl, OCOCH3, and ONO2. Linear relationships exist between the methylene J(13CH) and 2J(HgH), 4J(HgC) and 2J(HgC) and 3J(HgC); but deviations from linearity occur for the chloride, bromide, acetate, and nitrate in the relationships between 2J(HgH) and 4J(HgH), 2J(HGH) and 2J(HGC). These deviations are discussed in terms of hyperconjugative pπdπ bonding between the methylene CH bonds and mercury. 相似文献
999.
Titrimetric and spectrophotometric methods have been developed for the estimation of phosphite at mmole and mumole levels, respectively. Thallium(III) is used as an oxidant and the thallium(I) produced is determined either oxidimetrically with potassium bromate or by measurement of the absorbance of thallium(III) at 260 nm in the presence of 0.1 M hydrochloric acid and 1 M perchloric acid. Based on the fact that phosphite and oxalate are oxidized under different conditions, methods are described for the analysis of binary mixtures of phosphite and oxalate. A method is also described for estimation of thallium(III) with phosphite as reluctant, and is applied for analysis of mixtures of thallium(I) and thallium(III). 相似文献
1000.
Potassium bisoxalato diaquothallate(III) dihydrate is obtained by precipitating thallium(III) with oxalic acid from slightly acidic (HNO3 or H2SO4) solutions in the presence of potassium ions. The thermal decomposition behaviour of the complex is studied using the techniques of TG, DTA and DTG. The solid complex salt and the intermediate products of its thermal decomposition are characterised using IR absorption spectra, microscopic observations, electrical conductivity measurements and X-ray diffraction data. 相似文献