Chiral lithium amide
WebThese chiral lithium amides (la-i) can be prepared in both enantiomeric forms starting from the corresponding optically active amino acids that are available commercially. 1487 . 1488 K. KOGA Since it is known that lithium amide is actively involved at the transition state of deprotonation reaction of a WebThese results suggest that the lithium amide derived from (241) is a more effective chiral auxiliary than the amine itself. In fact, if the reaction is carried out with excess n -butyllithium, along with a corresponding amount of the achiral diisopropylamine, the yield is excellent and the diastereomeric excess is a very respectable 68% ( Table ...
Chiral lithium amide
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WebChiral enantioenriched organolithiums could also be prepared by deprotonation of prochiral substrates either using a chiral lithium amide or an alkyllithium in the presence of a chiral ligand. The deprotonation tactic is also useful for lithiation of aromatic rings at a proximal (or remote) site with respect to a “Directing Metalation Group ... WebSeven selected chiral mono-, di-, and tridentate amines supported on insoluble polymer were effectively prepared from corresponding primary amines or secondary amino alcohols and Merrifield resin. The reaction of the polymer-supported amines with excess n-butyllithium gave the corresponding lithium amide bases, which were tested in the aldol …
WebAn efficient enantioselective alkylation reaction at the α-position of cyclic ketones () can be realized in up to 92% enantiometric excess (e.e.) by first forming their lithium enolates using a chiral lithium amide in the presence of lithium bromide, followed by … WebAn enantioselective Meerwein-Ponndorf-Verley-type reduction of ynenoylsilanes by a chiral lithium amide followed by a Brook rearrangement and anti-mode protonation across …
WebOct 24, 2012 · Experiments involving competition between chiral and achiral lithium amides provide a qualitative impression of the kinetics of different amide motifs in enolization reactions. The level of enantioselectivity was not diminished by the inclusion of lithium diisopropylamide (LDA; see scheme) into asymmetric enolizations mediated by a … WebSep 27, 2024 · Chiral lithium amide bases allow the desymmetrisation of prochiral substrates and the production of enantiomerically enriched products, which are vital for …
WebMay 13, 2013 · 1. Introduction. The dimethyl ether of (R,R)- and (S,S)-1,2-dihydroxy-1,2-diphenylethane 1 is a powerful and widely applicable chiral external ligand 1 for asymmetric reactions of lithiated reagents, such as organolithium, 2 lithium enolate, and lithium amide. 3 Since the first report on the utility of chiral diether 1 in the catalytic and stoichiometric …
Chiral lithium amides may be used to effect the selective removal of one of two enantioselective protons in prochiral substrates. In the vast majority of cases, high enantioselection depends on the presence of a coordinating heteroatom in the prochiral substrate. Coordination between lithium and the … See more Provided the substrate is not sensitive to strong base and contains an appropriately positioned coordinating group, the scope of reactions of chiral lithium amides is quite wide. This … See more A number of alternative reagents for enantioselective deprotonation and functionalization are known. For example, chiral magnesium … See more Enantioselective deprotonations are typically employed in the early stages of synthesis, when starting materials are unlikely to be sensitive to base. Despite the requirement of … See more high school the musical the series charactersWebSince Whitesell[1] successfully applied a chiral lithium amide to enantioselective epoxide opening in 1980, the chemistry of chiral lithium amides has been greatly extended. … how many courts are there at apex levelhow many courts are in australiaWebChiral Lithium Amide Bases One of the most commonly employed reactions in organic synthesis involves the formation of a reactive carbon nucleophile by a metallation process. We have been examining “asymmetric deprotonation” chemistry using chiral lithium amides, which are essentially chiral variants of the commonly used lithium high school ticket softwareWebThe use of chiral lithium amides in the desymmetrisation of N-trialkylsilyl dimethyl sulfoximines. Chiral base desymmetrisation of dimethyl sulfoximines could provide a … high school ticket salesWebDec 20, 2016 · An overview on the structural arrangements adopted by Chiral Lithium Amides (CLAs), alone or in mixed complexes, is presented. These species are important … how many court reporters are there in the usWebApr 14, 2024 · Amides are one of the most important functional groups in organic chemistry and play essential roles in both the pharmaceutical industry and life sciences. However, due to the natural reactivity of carboxylic acids and amines, their direct coupling is challenging and often leads to reactions that are not atom-economic and produce large amounts ... how many courts in canada