Addition of Organozinc Reagents to Aldehydes

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. 

Addition of Organozinc Reagents to Aldehydes, Ketones, and a-Ketoesters 383... 

Addition of Organozinc Reagents to Aldehydes, Ketones, and a-Ketoesters 2.06.16.2.1 Chiral ligands used in addition reactions of diorganozincs with aldehydes... 

The chiral f5-dialkylamino alcohol DAIB serves as an efficient asymmetric catalyst for the addition of organozinc reagents to aldehydes. The reaction of diethylzinc with benzaldehyde in the presence of 2 mol % of (2S)-(-)-DAIB to give (S)-1-phenyl-1-propanol in 89% ee is described in the procedure which follows. DAIB exhibits the... 

K. Soai and S. Niwa, Enantioselective addition of organozinc reagents to aldehydes, Chem. Rev. 

Ligand evaluation continues for enantioselective addition of organozinc reagents to aldehydes, including the substituted BINOL 34, the ferrocene derivative 35, an imine 36 from 2-amino-1,2,2-triphenylethanol, as well as the Cj-symmetric 37 and enf-38. ... 

The tremendous success in the catalytic asymmetric addition of organozinc reagents to aldehydes spurred Itsuno and co-workers to examine the reactivity of diethylzinc with silyl imines in the presence of chiral amino alcohols and diols. Unfortunately, this type of azomethine function failed to react [23a]. The use of activated N-acyl- and iV-phosphinoylimines turned out to be crucial as evidenced by the following reports on the alkylation of these functions using di-... 

Many other aminoalcohols and related compounds have been recommended as catalysts in enantioselective additions of organozinc reagents to aldehydes. Tri-carbonyl chromium complexation of the aryl ring of 1.14 (R = Me,n-Bu) can lead to improved enantioselectivities [1171], Other arenechromium carbonyl com-plexed aminoalcohols have also been proposed as Zn ligands [1172],... 

For example Hatano, M., Miyamoto, T. and Ishihara, K. (2005) Enantioselective addition of organozinc reagents to aldehydes catalyzed by 3,3 -bis(diphenylphosphinoyl)-BINOL. Advanced Synthesis and Catalysis, 347 1561-1568. 

The asymmetric addition of organozinc reagents to aldehydes is one of the most thoroughly studied and successful enantioselective processes. While chiral ligand selection is much more delicate for the Zr-Zn system, due to the fast background addition reaction mediated by the achiral zirconocene that is present in stoichiometric amounts in the reaction mixture, chiral allylic alcohols can be obtained in >92% when amino thiols are used as chiral inducers (Scheme 12.7)... 

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