Asymmetric Aldol Reaction Using Chiral Sulfonamide Ligands

By: William Sommer, Aldrich ChemFiles 2008, 8.6, 9.

Aldrich ChemFiles 2008, 8.6, 9.

Walsh and co-workers developed a chiral diamine ligand used in the alkylation, arylation and vinylation of ketones under high enantiocontrol.1 The activity of this new ligand toward the vinylation of ketones has been demonstarted using a variety of vinylzinc intermediates. These vinylzinc reagents are generated by the hydrozirconation of terminal alkynes with Schwartz’s reagent, followed by transmetallation to zinc. This intermediate is then reacted with the aldehyde in the presence of the Ti(Oi-Pr)4, ZnMe2 and the chiral diamine ligand. The final chiral vinyl alcohol is generated with good to excellent yields and good enantioselectivities. This new ligand affords several distinct advantages over the prior art in the field including: low catalyst loading (up to 1 mol%), room temperature reactions complete in 24–36 h and high ee’s generated in gram scale reactions.


Scheme 1.

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Materials

     

References

  1. Li, H. et al. J. Am. Chem. Soc. 2005, 127, 8355

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