WebApr 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 ... 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 …
Stereoretentive enantioconvergent reactions
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 Webstereoretentive-enantioconvergent aza-Darzens reaction achieved using chiral lithium amides. The heterochiral selectivity was rationalised as a result of a bis-lithium, cationic Zimmerman–Traxler-type transition state 3 for the addition step.20 Having realised our first goal of achieving a direct stereoretentive-enantioconvergent chirs ma
Asymmetric synthesis mediated by chiral ligands
WebSep 27, 2024 · Chiral lithium amide bases allow the desymmetrisation of prochiral substrates and the production of enantiomerically enriched products, which are vital for the pharmaceutical industry and the total synthesis of natural products. Chapter 1 gives a brief review of this area and the progress that has been achieved over the last three decades. WebChiral amines have found widespread application in asymmetric synthesis serving, for instance, as chiral bases in enantioselective deprotonation reactions 1,2 or being valuable substances for resolving racemic mixtures of acids. Additionally, chiral amines are prevalent, essential parts of many drugs and drug candidates. α-Ethylbenzylamine WebFeb 1, 2007 · A novel type of chiral lithium amide base reaction, involving the rearrangement of certain types of symmetrical ring-fused episulfoxides, gives alkenyl sulfoxide products in up to 88% ee. graphing solutions calculator