نتایج جستجو برای: asymmetric catalyst
تعداد نتایج: 108514 فیلتر نتایج به سال:
A carboxy-directed asymmetric hydrogenation of α-alkyl-α-aryl terminal olefins was developed by using a chiral spiro iridium catalyst, providing a highly efficient approach to the compounds with a chiral benzylmethyl center. The carboxy-directed hydrogenation prohibited the isomerization of the terminal olefins, and realized the chemoselective hydrogenation of various dienes. The concise enanti...
Pd/bisphosphines complexes are highly effective catalysts for asymmetric hydrogenation of activated imines in trifluoroethanol. The asymmetric hydrogenation of N-diphenylphosphinyl ketimines 3 with Pd(CF3CO2)/(S)-SegPhos indicated 87-99% ee, and N-tosylimines 5 could gave 88-97% ee with Pd(CF3CO2)/(S)-SynPhos as a catalyst. Cyclic N-sulfonylimines 7 and 11 were hydrogenated to afford the useful...
Asymmetric hydrogenation uses inexpensive, clean hydrogen gas and a very small amount of a chiral molecular catalyst, providing the most powerful way to produce a wide array of enantio-enriched compounds in a large quantity without forming any waste. The recent revolutionary advances in this field have entirely changed the synthetic approach to producing performance chemicals that require a hig...
The synthesis of (3E)-1-benzyl-3-[(2-oxopyridin-1(2H)-yl)methylidene]piperidine-2,6-dione 5 from N-benzylglutarimide was achieved in three steps. The asymmetric hydrogenation of 4 gave either the product of partial reduction (10) or full reduction (13), depending on the catalyst which was employed, in high ee in each case. Attempts at asymmetric transfer hydrogenation (ATH) of resulted in forma...
In this account, we describe the design, synthesis and applications of tethered versions of the Ru(II)/N-tosyl-1,2-diphenylethylene-1,2-diamine (TsDPEN) class of catalyst that are commonly used for asymmetric transfer hydrogenation and asymmetric hydrogenation of ketones and imines. The review covers key aspects of the reaction mechanisms and examples of applications, including industrial appli...
The development of new catalytic asymmetric reactions continues to be a major goal in organic chemistry. Here we report a novel antibody-catalyzed intramolecular Michael addition of aldehydes and ketones to enones. The reaction is enantioselective and diastereoselective with a high ee value and cis/trans ratio. This is the first example of asymmetric intramolecular Michael addition of ketones. ...
We report a catalytic asymmetric reaction process that involves the use of solid-phase reagents and catalysts that constitute the packing of a series of "reaction columns". This process was applied to the catalytic asymmetric synthesis of beta-lactams, to yield pure products with excellent enantio- and diastereoselectivity. We have identified several advantages to conducting chemical reactions ...
The promising performance of copper(II) complexes was demonstrated for asymmetric boron conjugate addition to α,β-unsaturated nitriles in water. The catalyst system, which consisted of Cu(OAc)2 and a chiral 2,2'-bipyridine ligand, enabled β-borylation and chiral induction in water. Subsequent protonation, which was accelerated in aqueous medium, led to high activity of this asymmetric catalysis...
The development of a catalytic asymmetric method for the direct aminoallylation of aldehydes is described that gives high asymmetric inductions for a broad range of substrates including both aromatic and aliphatic aldehydes. This method allows for direct isolation of unprotected analytically pure homoallylic amines without chromatography. The unique catalyst system developed for this process in...
4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isoc...
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