نتایج جستجو برای: selectivity of products

تعداد نتایج: 21179743  

Journal: :Organic & biomolecular chemistry 2012
Xiaohong Wei Feng Wang Guoyong Song Zhengyin Du Xingwei Li

[RhCp*Cl(2)](2) can catalyze the oxidative coupling of secondary isonicotinamides with activated olefins using Cu(OAc)(2) as an oxidant. The selectivity can be controlled by the solvent. In MeCN, the mono-olefination and two-fold oxidation reaction is the major pathway, while in THF this reaction gave mostly diolefination products. In both cases, the coupled products contain an exocyclic C=C bond.

M. Vadi

The catalyst Pt-Ta supported on 7-alumina was prepared by impregnation with solution containing compoundsof II21K1.0. and Ta205 The Pt concentration was kept constant at 0.2 vet% while the concentration of thetantalum was 0,4 wt%. The activity and selectivity of catalyst were determined under conditions at 450-500 °Cand 15-30 atm.. with molar ratio H2/C[H,e5 and WH=1.5mL/h for converted n-hepta...

2013
Jiaqi Cheng Kristin M. Poduska

We demonstrate a simple strategy to either prevent or enhance hydroxide incorporation in nanocrystalline solid-state metathesis reaction products prepared in ambient environments. As an example, we show that ZnCO3 (smithsonite) or Zn₅(CO₃)₂(OH)₆ (hydrozincite) forms extremely rapidly, in less than two minutes, to form crystalline domains of 11 ± 2 nm and 6 ± 2 nm, respectively. The phase select...

Journal: :Chemical & pharmaceutical bulletin 2002
Yumiko Nomura Mayu Iguchi Hirohisa Doi Kiyoshi Tomioka

The asymmetric reaction of a lithium enolate generated from a BHA (2, 6-di-tert-buty-4-methoxyphenyl) propanoate was allowed to react with benzaldehyde in the presence of a diether-type chiral ligand affording the corresponding anti-aldol product in a moderate enantioselectivity. A tetradentate ligand induced better enantioselectivity albeit relative loss of anti-selectivity. A variation of lit...

Journal: :Journal of the American Chemical Society 2011
Lada Klaić Paul C Trippier Rama K Mishra Richard I Morimoto Richard B Silverman

Celastrol, an important natural product and Hsp90 inhibitor with a wide range of biological and medical activities and broad use as a biological probe, acts by an as yet undetermined mode of action. It is known to undergo Michael additions with biological sulfur nucleophiles. Here it is demonstrated that nucleophiles add to the pharmacophore of celastrol in a remarkable stereospecific manner. E...

Journal: :Journal of the American Chemical Society 2013
Elizabeth T Kiesewetter Robert V O'Brien Elsie C Yu Simon J Meek Richard R Schrock Amir H Hoveyda

The first examples of catalytic cross-metathesis (CM) reactions that furnish Z-(pinacolato)allylboron and Z-(pinacolato)alkenylboron compounds are disclosed. Products are generated with high Z selectivity by the use of a W-based monoaryloxide pyrrolide (MAP) complex (up to 91% yield and >98:2 Z:E). The more sterically demanding Z-alkenylboron species are obtained in the presence of Mo-based MAP...

2005
Keith Smith Gamal A. El-Hiti

Zeolite catalysts can play an important role in the development of greener organic syntheses through their abilities to act as heterogeneous catalysts, support reagents, entrain by-products, avoid aqueous work-ups and enhance product selectivities via shape-selectivity. We have shown that zeolites under modest conditions can have advantages in para-regioselective nitration, alkylation, acylatio...

2000

Introduction Digital Signal Processing (DSP) affords greater flexibility, higher performance (in terms of attenuation and selectivity), better time and environment stability and lower equipment production costs than traditional analog techniques. Additionally, more and more microprocessor circuitry is being displaced with costeffective DSP techniques and products; an example of this is the emer...

Journal: :Catalysts 2023

An improved para-selective C(sp2)-H borylation of anisole derivatives is described. The selective probably dominated by the change in electron density on aromatic ring when a Lewis acid coordinated with an substrate. In addition, sterically hindered bipyridyl ligand used reaction also favors para-selectivity. With this strategy, it has been demonstrated that ratio para-borylated products could ...

Journal: :Chemistry 2005
Thomas R Ward

Enzymatic and homogeneous catalysis offer complementary means to produce enantiopure products. Incorporation of achiral, biotinylated aminodiphosphine-rhodium complexes in (strept)avidin affords enantioselective hydrogenation catalysts. A combined chemogenetic procedure allows the optimization of the activity and the selectivity of such artificial metalloenzymes: the reduction of acetamidoacryl...

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