Strained silacycle-catalyzed asymmetric Diels–Alder cycloadditions: the first highly enantioselective silicon Lewis acid catalyst
摘要:
The first highly enantioselective silicon Lewis acid catalyst for an asymmetric organic transformation has been developed. The catalyst derives its activity from the strain induced in the silicon center by virtue of being constrained in a five-membered ring. A simple tridentate ligand has been developed and the derived chlorosilane complex catalyzes the Diels-Alder cycloaddition of methacrolein and cyclopentadiene with 94% ee. (c) 2006 Elsevier Ltd. All rights reserved.
A New Cationic, Chiral Catalyst for Highly Enantioselective Diels−Alder Reactions
作者:Kevin T. Sprott、E. J. Corey
DOI:10.1021/ol034706k
日期:2003.7.1
[reaction: see text] The Diels-Alder reaction of cyclopentadiene and 2-methacrolein is catalyzed by a chiral Lewis acid to form the exo adduct in 96% yield and 96% ee.
Highly Enantioselective [4 + 2] Cycloaddition Reactions Catalyzed by a Chiral <i>N</i>-Methyl-oxazaborolidinium Cation
作者:Eda Canales、E. J. Corey
DOI:10.1021/ol8011502
日期:2008.8.7
The reaction of lithium aryl borohydrides with salts of beta-amino alcohols provides a new route for the synthesis of oxazaborolidines. This method also leads to the first synthesis of hitherto elusive N-methyl oxazaborolidine cations, specifically the cationic proline derivative 3. Compound 3 is a strong chiral Lewis acid which is very effective for catalysis of [4 + 2]-cycloaddition reactions in good yield and with high enantioselectivity. Several diverse examples illustrate the scope of these catalytic reactions.
Bronsted Acid Assisted Chiral Lewis Acid (BLA) Catalyst for Asymmetric Diels-Alder Reaction