MEYERS Asymmetric synthesis

MEYERS Asymmetric synthesis Chiral oxaioles in asymmetric synthesis of cartxixylic acids, aldehydes, chiral dihydronaphthalenes. 

In recent years there has been a proliferation of new reactions and reagents that have been so useful in organic synthesis that often people refer to them by name. Many of these are stereoselective or regioselecth/e methods. While the expert may know exactly what the Makosza vicarious nucleophilic substitution, or the Meyers asymmetric synthesis refers to, many students as well as researchers would appreciate guidance regarding such "Name Reactions". 

Reviews on stoichiometric asymmetric syntheses M. M. Midland, Reductions with Chiral Boron Reagents, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 2, Chap. 2, Academic Press, New York, 1983 E. R. Grandbois, S. I. Howard, and J. D. Morrison, Reductions with Chiral Modifications of Lithium Aluminum Hydride, in J. D. Morrison, ed.. Asymmetric Synthesis, Vol. 2, Chap. 3, Academic Press, New York, 1983 Y. Inouye, J. Oda, and N. Baba, Reductions with Chiral Dihydropyridine Reagents, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 2, Chap. 4, Academic Press, New York, 1983 T. Oishi and T. Nakata, Acc. Chem. Res., 17, 338 (1984) G. Solladie, Addition of Chiral Nucleophiles to Aldehydes and Ketones, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 2, Chap. 6, Academic Press, New York, 1983 D. A. Evans, Stereoselective Alkylation Reactions of Chiral Metal Enolates, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 3, Chap. 1, Academic Press, New York, 1984. C. H. Heathcock, The Aldol Addition Reaction, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 3, Chap. 2, Academic Press, New York, 1984 K. A. Lutomski and A. I. Meyers, Asymmetric Synthesis via Chiral Oxazolines, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 3, Chap. 

MEYERS Asymmetric synthesis Chsal oxazoles in asymmetric synthesis of carboxylic acids, aldehydes, chual dihydrona(Aithalenes. 

The studies of the reactivity of saturated pyrrolo[2,l- )oxazoles are in general associated with the reactivity of Meyers chiral bicyclic lactams and their applications in asymmetric synthesis. 

In fact, the usefulness of chiral oxazoline enolates in asymmetric synthesis had been already demonstrated by Meyers [24]. Evans obtained enantiofacial selectivities (or enantiomeric excesses = e.e) equal to or greater than 99% (Table 9.4). 

Chiral oxazolines (242), which had been originally used by Meyers et al. for asymmetric synthesis, were also applied for the asymmetric transformation of 2-chloro-alkanoic acids to produce chiral 2-chloroalkanenecarboxylic acids in 45-73 % optical yield245). 

In the mid-seventies, with the development of generally applicable stoichiometric asymmetric syntheses, especially the Meyers oxazoline methodology as the first one, the scientific community began to believe that asymmetric synthesis really worked resulting in an explosive growth of this new field. Later on, and mainly driven by the fact that the biological activity of enantiomers is usually different, dozens of new chemical companies were founded all over the world in a newly created area called chirotechnology . 

For a review of asymmetric synthesis via chiral oxazolines, see Lutomski Meyers, in Morrison. Ref. 1467, pp. 213-274. 

Albert 1. Meyers and Daniel Berney 55 ASYMMETRIC SYNTHESIS OF 4,4-DIALKYLCYCLOHEXENONES FROM CHIRAL BICYCLIC LACTAMS (R)-4-ETHYL-4-ALLYL-2-CYCLOHEXEN-1-ONE... 

Meyers, A. I. Knaus, G. Kendall, P. M. Synthesis via oxazobnes IX. An asymmetric synthesis of 2-methoxy and 2-chloroalkanoic acids. Tetrahedron Lett. 1974, 39, 3495-3498. 

In another work, Meyers and coworkers found that in asymmetric synthesis of macrocyclic ketones and a-alkyl ketones by using chiral imines, two intermediate lithioenamines were obtained. One of them was formed in the reaction with LDA at — 30 C and is the kinetically controlled is-isomer 36. The second product formed on reflux with LDA is the Z-isomer 37, which is the thermodynamically more stable isomer. Both formed anion 38 on heating (equation 10). 

Similar amidoester groups offered Meyers and coworkers new abilities, especially in asymmetric synthesis. The systems discussed here are 1,3-oxazolinic systems that are... 

Chiral Bicyclic Lactams Useful Precursors and Templates for Asymmetric Synthesis. Meyers, A. L Brenget, G. P. Chem. Commun, 1997, 1. 

Asymmetric synthesis of ketones (7, 17). Meyers and Williams have extended the asymmetric alkylation of cyclohexanones via the imines formed from 1 to acyclic ketones. Initially optical yields were only 3-44%, but they can be increased to 20-98% by heating the lithioenamines to reflux (THF) prior to alkylation at -78°. Evidently the lithioenamines formed at —20° are mixtures of (E)- and (Z)-isomers. The optical yields are lowered as the size of substituents on the ketone increases. Example ... 

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