Amidation enantioselective

The study on micellar models is still at the beginning. An amphiphilic ligand which can form micelles by itself has not yet been prepared. It is necessary to obtain complexes of higher stability in order to activate the hydroxyl group strong enough in the reactions of inactive esters or amides. Enantioselectivity must reach higher specifity. Nevertheless it seems to be clear that many features or some important clues have already been disclosed for further refinements of this micellar systems. More details about the present micellar reactions will be reported elsewhere in near future. 

Carboxylic acid, ester, amide Enantioselective, multiple centers 6, 51,63, 114, 116, 117, 153, 163, 166, 200 Ketone... 

CH2I2, Et2Zn, chiral disulfon-amide (enantioselective)... 

Biotransformations of hve-membered alicyclic trani-A-protected-amino nitriles proceeded faster than in case of six-membered compounds. The products of the trani-A-protected-amino nitriles (amides and acids) were formed preferentially than the products of the c A-counterparts (only amides). Enantioselectivities were strongly dependent on the structure the trani-hve-membered substrates gave exclusively amides with excellent optical purity (94-99%), in contrast to the tran -six-membered substrates resulted in the formation of the acid with excellent enantiopurity (87-99%). The corresponding c A-compounds yielded much lower enantiomeric excesses. Nitrile precursor of a-methylene-P-amino acids was analogously investigated (Winkler et al., 2005) (Table 17.13). 

CH2I2, Et2Zn, chiral disulfon-amide (enantioselective) CH2I2, Et2Zn, chiral dioxaborolane (enantio-selective)... 

The diastereoselective lithiation of 74 shows that ferrocenes bearing electron-withdrawing directors of lithiation are sufficiently acidic to allow deprotonation with lithium amide bases. By replacing LDA with a chiral lithium amide, enantioselectivity can be achieved in some cases. The phosphine oxide 82, for example, is silylated in 54% ee by treatment with N-Hthiobis(a-methylbenzyl)amine 83 in the presence of Me3SiCl (Scheme 20) [58]. 

There are many classes of substrate structures involved in heterogeneous enantioselective hydrogenation on modified metal catalysts. They consist of 2-oxocarboxylic acids and their esters, ketones, diketones, keto lactones, imsaturated acids, oximes, and amides. Enantioselectivities of heterogeneous chirally modified metal catalysts are determined in an important way by the matched interactions between die functional groups of the substrate and the modifier. 

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