Catalytic Asymmetric Synthesis of Chiral Tertiary Organoboronic Esters through Conjugate Boration of β-Substituted Cyclic Enones
The first catalytic enantioselective conjugate boration of β-substituted cyclic enones was developed to produce enantiomerically enriched tertiary organoboronates. The optimized asymmetric catalyst includes a QuinoxP*-CuO t Bu complex generated from CuPF6(CH3CN)4 and LiO t Bu. In situ generated LiPF...
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Published in | Journal of the American Chemical Society Vol. 131; no. 33; pp. 11664 - 11665 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
WASHINGTON
American Chemical Society
26.08.2009
Amer Chemical Soc |
Subjects | |
Online Access | Get full text |
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Summary: | The first catalytic enantioselective conjugate boration of β-substituted cyclic enones was developed to produce enantiomerically enriched tertiary organoboronates. The optimized asymmetric catalyst includes a QuinoxP*-CuO t Bu complex generated from CuPF6(CH3CN)4 and LiO t Bu. In situ generated LiPF6 significantly increased product yield. The enantioselectivity, however, was almost constant irrespective of the alkali metal used (Li, Na, or K). Moreover, a protic additive, which was essential in the previous Cu-catalyzed enantioselective boration to linear β-monosubstituted substrates (Yun’s reaction), was not necessary. The substrate scope was broad, and high to excellent enantioselectivity was produced using both β-aromatic and aliphatic (linear and branched)-substituted cyclic enones with five-, six-, and seven-membered ring sizes. Due to the synthetic versatility of organoboron compounds, a variety of new chiral building blocks containing a chiral tetrasubstituted carbon was synthesized based on this methodology. Specifically, a one-pot three-component reaction from α,β-substituted cyclic enone, bis(pinacolato)diboron (PinB-BPin: 2), and an aldehyde proceeded with a high level of enantio- and diastereocontrol. These chiral building blocks are difficult to access using other methods. |
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Bibliography: | KAKEN ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0002-7863 1520-5126 |
DOI: | 10.1021/ja9045839 |