Submit Manuscript  

Article Details


Synthesis of 1,2-Diamine Bifunctional Catalysts for the Direct Aldol Reaction Through Probing the Remote Amide Hydrogen

[ Vol. 6 , Issue. 2 ]

Author(s):

Rajasekhar Dodda, Sampak Samanta, Matthew Su and John C.-G. Zhao*   Pages 171 - 176 ( 6 )

Abstract:


Background: While proline can catalyze the asymmetric direct aldol reactions, its catalytic activity and catalyst turnover are both low. To improve the catalytic efficiency, many proline-based organocatalysts have been developed. In this regard, prolinamide-based bifunctional catalysts have been demonstrated by us and others to be highly efficient catalysts for the direct aldol reactions.

Methods: By carefully adjusting the hydrogen bonding ability of the remote β-amide hydrogen of the 1,2-diamine-based prolinamide bifunctional catalysts, the catalytic activity and the asymmetric induction of these catalysts were significantly improved for the direct aldol reaction between aldehydes and enolizable ketones.

Results: Using the β-acetamido- and β-tosylamidoprolinamide catalysts, the highly enantio- and diastereoselective direct aldol reactions between enolizable ketones and aldehydes were achieved (up to >99% ee, 98:2 dr). A low catalyst loading of only 2-5 mol % of β-tosylamidoprolinamide catalyst was needed to obtain the desired aldol products in good to high yields and high stereoselectivities.

Conclusion: Some highly efficient 1,2-diamine-based bifunctional prolinamide catalysts have been developed through probing the remote β-amide hydrogen for its hydrogen bonding capability. These catalysts are easy to synthesize and high enantioselectivities may be achieved at very low catalyst loadings.

Keywords:

Aldol, amide, asymmetric, bifunctional, catalysis, hydrogen bonding, proline.

Affiliation:

Department of Chemistry, University of Texas at San Antonio, One UTSA Circle. San Antonio, Texas 78249-0698, Department of Chemistry, University of Texas at San Antonio, One UTSA Circle. San Antonio, Texas 78249-0698, Department of Chemistry, University of Texas at San Antonio, One UTSA Circle. San Antonio, Texas 78249-0698, Department of Chemistry, University of Texas at San Antonio, One UTSA Circle. San Antonio, Texas 78249-0698



Read Full-Text article