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21.
Maria Merces Marques C. Costa F. Lemos F. Ram?a Ribeiro A. R. Dias 《Reaction Kinetics and Catalysis Letters》1997,62(1):9-15
In this paper we present a kinetic approach to the analysis of steady-state homogeneous Ziegler-Natta polymerization activity
data. The influence of the number of monomeric species that are coordinated to the active site on the apparent rate law is
discussed and the equations are fitted to the experimental results. 相似文献
22.
相转移催化元素硫的歧化反应 总被引:1,自引:0,他引:1
本工作将相转移催化(PTC)应用于元素硫歧化反应,大大降低了反应温度,提高了反应速度。该反应被证实与熔态硫在水溶液中的歧化相同,即4S+6OH~-=2S~(2-)+S_2O_3~(2-)+3H_2O。比较了四乙基铵、四丁基铵、十六烷基三甲基铵和三辛基甲基铵四种相转移催化剂及四氯乙烯、二甲苯和四氯乙烷三种溶剂的影响。讨论了本体系相转移催化的证据。为改进以元素硫歧化反应为基础的提取冶金过程提供了依据。 相似文献
23.
Acetylation of alcohols with an equivalent amount of acetic anhydride is feasible in the presence of fluorous distannoxane catalyst in heterogeneous single fluorous system. The fluorous layer containing catalyst can be recycled and reused at least 10 times. 相似文献
24.
Adriana Ionescu 《Journal of organometallic chemistry》2006,691(18):3806-3815
The ω-hydroxyolefins 3-buten-1-ol, 3-buten-1-methyl-1-ol and 4-penten-1-ol were subjected to hydroxycarbonylation conditions in water in the presence of PdCl2(PhCN)2 and 4-8 equiv. of water soluble tris(3-sodiumsulfonatophenyl)phosphine (TPPTS), or N-bis(N′,N′-diethyl-2-aminoethyl)-4-aminomethylphenyl-diphenylphosphine (N3P). Under conditions of high conversion, the olefins primarily undergo isomerisation through a chain walking mechanism with selectivities for aldehyde ranging from 65% to 98%, with the lower values for longer chain alcohols. The lactones formed as the minor product are almost exclusively branched, indicating that in the first step 2,1-insertion is strongly favoured over 1,2-insertion. In the N3P system also linear lactone is produced at lower conversion. Running the reaction in D2O produces multiple deuterium incorporation in all positions of the carbon chain. A mechanism is discussed. 相似文献
25.
An efficient asymmetric synthesis of selective estrogen receptor β-modulator (S)-4-bromo-9a-butyl-8-chloro-6-fluoro-7-hydroxy-1,2,9,9a-tetrahydro-fluoren-3-one was developed. The route features a chemoselective aromatic chlorination reaction, an asymmetric phase-transfer-catalyzed alkylation of an indanone with efficient ee upgrade by racemate crystallization, and a robust bromination reaction using imidazole as an in situ bromine trap to avoid overreaction. The synthesis proceeds in 34% yield over 8 steps from 2-fluoroanisole, and provides material with >99.5% ee. 相似文献
26.
Jong-Ho Kim 《Tetrahedron letters》2004,45(30):5827-5831
A poly(imidazoliummethyl styrene)-surface grafted-polystyrene resin was prepared by suspension polymerization. This was used as the polymer-supported carbene precursor for the palladium complex, which efficiently catalyzed the Suzuki cross-coupling of aryl halides and phenylboronic acid. 相似文献
27.
Matthew T. AllinghamAndrew Howard-Jones Patrick J. MurphyPeter W.R. Caulkett 《Tetrahedron letters》2003,44(48):8677-8680
The preparation of the tetracyclic C2-symmetric guanidinium salts 5 and 11-13 is reported together with their application to enantioselective transformations. 相似文献
28.
2,2-Dimethyl-3-(2-methyl-3-indolyl)cyclopropylacetic acid, its amide and esters, and the corresponding alcohol, viz., the product of ester reduction by LiAlH4, were synthesized. The chemoselectivity of N- and O-alkylation of these compounds was studied. Selective monoalkylation at the nitrogen atom of the heterocycle, O-alkylation to the side chain, or dialkylation at both nucleophilic sites can be carried out under conditions of phase-transfer catalysis. The N-acylation at the indole fragment of nitrile of this acid occurs only under the Vilsmeier—Haak formylation conditions. 相似文献
29.
Naotomo Dobashi 《Tetrahedron letters》2007,48(27):4669-4673
Palladium-1,2-bis(diphenylphosphino)ethane complex catalyzes regioselective Markovnikov addition of diphenylphosphine oxide to terminal alkynes in propionitrile, while the use of triarylphopshines, di(o-tolyl)phenylphosphine in particular, as the ligand leads to dehydrogenative double addition forming 1,2-diphenylphosphinyl-1-alkenes as major products. 相似文献
30.
V. A. D’yakonov R. K. Timerkhanov A. G. Ibragimov U. M. Dzhemilev 《Russian Chemical Bulletin》2007,56(11):2232-2235
Catalytic cycloalumination of cyclonona-1,2-diene upon treatment with Et3Al and EtAlCl2 in the presence of Cp2ZrCl2, leading to 10-ethyl-10-aluminabicyclo[7.3.01,9]dodec-8-ene (1) and 11-ethyl-11-aluminatricyclo[10.7.01,12.02,10]nonadeca-9,12-diene, respectively, was accomplished in high yields. A possibility for the selective transformation of compound
1 to 1-allyl-9-(pent-4-enyl)cyclonon-1-ene and 10-hydroxybicyclo[7.3.01,9]dodec-8-ene in one preparative step was demonstrated.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2156–2159, November, 2007. 相似文献