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51.
T. Ashok Reddy M. Srinivasan 《Journal of polymer science. Part A, Polymer chemistry》1987,25(11):2987-3003
Several polyesters containing thiaxanthone rings were prepared from 2,7-dichloroformylthiaxanthone-5,5′-dioxide ( IVa ), 2,8-dichloroformylthiaxanthone-5,5′-dioxide ( IVb ), and bisphenols by solution polycondensation. The 2,8-diethoxycarbonylthiaxanthone-5,5′-dioxide ( V ) was prepared and characterized by spectral methods to confirm the formation of 2,8-thiaxanthonedicarboxylic acid-5,5′-dioxide ( IVb ). Prior to polymer synthesis two model compounds,2,7-diphenoxycarbonylthiaxanthone-5,5′-dioxide (MDE-1) and 2,8-diphenoxycarbonylthiaxanthone-5,5′-dioxide (MDE-2), were synthesized and characterized by spectral methods. The polyesters were obtained in 62–78% yield and had inherent viscosities in the range 0.42–0.90 dL/g. The effect of thiaxanthone rings on solubility, crystallinity, and thermal stability of the polyesters are also discussed. The polyesters have decomposition temperatures in the range 372–438°C. 相似文献
52.
An efficient and mild method for the reduction of aromatic nitro and azido groups on solid support using Al/NiCl2·6H2O and Al/NH4Cl is described. This solid phase reduction technique has been applied towards the synthesis of DNA binding pyrrolo[2,1-c][1,4]benzodiazepine antitumour antibiotics. 相似文献
53.
Venkatapuram Padmavathi Mudigonda Rajagopala Sarma Adivireddy Padmaja Dandu Bhaskar Reddy 《Journal of heterocyclic chemistry》2003,40(5):933-937
Novel 2‐pyrazolines were obtained by the cycloaddition of diazomethane to bis(arylsulfonylethenyl)‐sulfones ( 3 ) and 1‐arylsulfonyl‐2‐styrylsulfonylethenes (7). Dehydrogenation of 2‐pyrazolines with chloranil gave pyrazoles. 相似文献
54.
Ruthenium halides (Cl and Br) react with monotertiary arsines-Ph2RAs (R=Me, Et, Pr
n
) in methoxyethanol, in the presence of aq. formaldehyde to give monocarbonyl complexes of ruthenium(II) of the type RuX2(CO) (Ph2RAs)3. Carbonylation of an ethanolic solution containing ruthenium trichloride and the arsine at room temperature yieldtrans dicarbonyl compounds of the formula RuCl2(CO)2 (Ph2RAs)2. The osmium monocarbonyls OsX2(CO) (Ph2RAs)3 (X=Cl, Br; R=Me, Et) react with NaBH4 in methanol to yield complexes of the composition OsHX(CO) (Ph2RAs)3. The ruthenium analogues RuHCl(CO) (Ph2RAs)3 have also been made. Structures have been assigned to all these compounds on the basis of IR and NMR spectral results. 相似文献
55.
Sadagopan Raghavan A. RajenderM.Abdul Rasheed S.Ramakrishna Reddy 《Tetrahedron letters》2003,44(45):8253-8256
A novel, unprecedented transformation of δ-hydroxysulfoxides into substituted tetrahydrofurans by a silicon promoted Pummerer type reaction is disclosed. The transformation is shown to be general and is brought about under very mild reaction conditions. The products with the sulfide group at the anomeric carbon provide a suitable handle to carry out further transformations. 相似文献
56.
Interactive effects of ultraviolet-B radiation and temperature on cotton physiology, growth, development and hyperspectral reflectance 总被引:1,自引:0,他引:1
Current conditions of 2-11 kJ m(-2) day(-1) of UV-B radiation and temperatures of >30 degrees C during flowering in cotton cultivated regions are projected to increase in the future. A controlled environment study was conducted in sunlit growth chambers to determine the effects of UV-B radiation and temperature on physiology, growth, development and leaf hyperspectral reflectance of cotton. Plants were grown in the growth chambers at three day/night temperatures (24/16 degrees C, 30/22 degrees C and 36/28 degrees C) and three levels of UV-B radiation (0, 7 and 14 kJ m(-2) day(-1)) at each temperature from emergence to 79 days under optimum nutrient and water conditions. Increases in main stem node number and the node of first fruiting branch and decrease in duration to first flower bud (square) and flower were recorded with increase in temperature. Main effects of temperature and UV-B radiation were significant for net photosynthetic rates, stomatal conductance, total chlorophyll and carotenoid concentrations of uppermost, fully expanded leaves during squaring and flowering. A significant interaction between temperature and UV-B radiation was detected for total biomass and its components. The UV-B radiation of 7 kJ m(-2) day(-1) reduced boll yield by 68% and 97% at 30/22 degrees C and 36/28 degrees C, respectively, compared with yield at 0 kJ m(-2) day(-1) and 30/22 degrees C. No bolls were produced in the three temperature treatments under 14 kJ m(-2) day(-1) UV-B radiation. The first-order interactions between temperature, UV-B radiation and leaf age were significant for leaf reflectance. This study suggests a growth- and process-related temperature dependence of sensitivity to UV-B radiation. 相似文献
57.
AbstractA convergent synthesis of the southern furan segment of novel furanocembranoids from Croton oblongifolius has been accomplished involving silver-catalyzed cyclization of alkynyl diol as the key step towards 2, 5-disubstituted furan ring formation. 相似文献
58.
The polymerization of acrylonitrile (AN) initiated by oxygen-ascorbic acid (AA)-ferric ion system was studied in dil. HNO3 at 40°. The rate of polymerization, Rp, was found gravimetrically. In the [Fe3+] range, (2–5 × 10?5 M, Rp was proportional to [AN]1.5 ± 0.05, [O2]0.5 ± 0.02 [AA]0 and [Fe3+]0; for [Fe3+] = (5–30) × 10?5 M, it was proportional to [AN]1.8 ± 0.05, [O2]0.6 ± 0.02, [AA]0 and [Fe3+]?0.9 ± 0.05. A plausible reaction scheme is proposed and rate law presented to explain these results. Rp increased with ionic strength and [HNO3] (up to ~0.25 M). An initial rate increase with temperature followed by a decrease was noticed. Chain lengths of the polymers were determined viscometrically. 相似文献
59.
An enantioselective synthesis of (+)-prelactone B 1 has been achieved on a multigram scale starting from a known bicyclic precursor 2. The key feature of the strategy is the generation of 3-stereogenic centres from a single bicyclic precursor, which has been utilized as a chiral building block for the synthesis of various natural products. 相似文献
60.
A. V. Reddy M. L. P. Reddy Y. K. Reddy 《Journal of Radioanalytical and Nuclear Chemistry》1984,86(6):391-397
The extraction of cobalt/II/ from ammonium chloride-ammonium hydroxide buffer solutions of pH 6.5 by 2,4-dihydroxyacetophenone thiosemicarbazone /DATS/ in n-butanol has been studied. Cobalt/II/ forms 11 complex /metal:reagent/ with DATS. Addition of pyridine enhances the extraction. The influence of metal concentration and the effect of diverse ions on the extraction of cobalt/II/ have been investigated. 相似文献