Chiral Oxazaborolidine−Aluminum Bromide Complexes Are Unusually Powerful and Effective Catalysts for Enantioselective Diels−Alder Reactions
作者:Duan Liu、Eda Canales、E. J. Corey
DOI:10.1021/ja068637r
日期:2007.2.1
acid catalyst than protonated 1 (i.e., 2) for enantioselectiveDiels−Alderreactions. Only 4 mol % of catalyst 3 is required to achieve yields and enantiomeric purities of 90% over a broad range of achiraldienes and dienophiles. The ligand from which 3 is derived can be recovered easily and with high efficiency. The method is illustrated by 22 examples.
Lewis Acids as Activators in CBS-Catalysed Diels-Alder Reactions: Distortion Induced Lewis Acidity Enhancement of SnCl<sub>4</sub>
作者:Alexander R. Nödling、Robert Möckel、Ralf Tonner、Gerhard Hilt
DOI:10.1002/chem.201602394
日期:2016.9.5
correlation was found between the Δδ(2H) values and rate constants kDA, which indicates a direct translation of Lewis acidity into reactivity of the Lewis acid–CBS complexes. Unexpectedly, a significant deviation was found for SnCl4 as Lewis acid. The SnCl4–CBS adduct was much more reactive than the Δδ(2H) values predicted and gave similar reactionrates to those observed for the prominent AlBr3–CBS adduct
Self-assembled coordination cage 1 was found to accelerate Diels–Alderreactions in an aqueous media: e.g., 113-fold acceleration was observed in the reaction of isoprene with naphthoquinone.
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.