Organozinc enantioselectivity

Design of chiral catalysis and asymmetric autocatalysis for diphenyl-(l-methyl-pyrrolidin-2-yl) methanol-catalyzed enantioselective additions of organozinc reagents 97YGK994. 

Copper-catalyzed Enantioselective Conjugate Addition Reactions of Organozinc Reagents... 

Numerous chiral non-S-coordinating bis(sulfonamides) have been successfully involved in the enantioselective addition of various organozinc reagents to aldehydes since the first use of tr<2 5-l(i ),2(i )-bis(trifluoromethanesulfo-namido)cyclohexane reported in 1989 by Ohno et These authors demonstrated the usefulness of this ligand in the Ti-catalysed enantioselective addition of ZnR2 to a variety of aldehydes, allowing enantioselectivities of up to 99% ee to be obtained (Scheme 3.37). 

Even if hundreds of chiral catalysts have been developed to promote the enantioselective addition of alkylzinc reagents to aldehydes with enantioselectivities over 90% ee, the addition of organozinc reagents to aldehydes is not a solved problem. For example, only very few studies on the addition of vinyl groups or acetylides and even arylzinc reagents to aldehydes have been published, in spite of the fact that the products of these reactions, chiral allylic, propargylic and aryl alcohols, are valuable chiral building blocks. 

Feringa, B. L. Naasz, R. Imbos, R. Arnold, L. A. Copper-catalyzed Enantioselective Conjugate Addition Reactions of Organozinc Reagents. In Modem Organocopper Chemistry Krause, N. Ed. Wiley-VCH GmbH Weinheim, 2002 Chapter 7, pp 224—258. 

TADDOL 104 and 126 afford 95-99% ee in the asymmetric addition of organozinc reagents to a variety of aldehydes. The best enantioselectivities are observed when a mixture of the chiral titanium TADDOL compound 127 and excess [Ti(OPr1)4] are employed (Scheme 2-49). The mechanism of the alkylzinc addition involves acceleration of the asymmetric catalytic process by the... 

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