ORGN 56 |
| A new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH) is developed. Its chromium complex, TBOxCrCl, (3 mol%) effectively catalyzes the pinacol coupling reaction of aromatic aldehydes at room temperature with high yield (up to 94%), high diastereoselectivity (up to dl : meso = 98 : 2), and high enantioselectivity (up to 98%). The scope of the present method turns out not to be limited to aromatic aldehyde derivatives, as cyclohexanecarboxaldehyde undergoes pinacolization as well (44% yield, dl : meso = 93 : 7, 84% ee). The method provides an efficient access to enantioenriched 1,2-diols. The utility of the new chiral ligand, tethered bis(8-quinolinol) (TBOxH) is further explored. Its chromium complex, TBOxCr(III)Cl, effectively catalyzes the Nozaki-Hiyama allylation reactions of various aldehydes at room temperature with high yield (up to 95%), and high enantioselectivity (up to 99% ee). The scope of the present method is shown to be wide and this method represents an efficient access to chiral homoallylic alcohols. |
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H. C. Brown Legacy Symposium
1:30 PM-5:00 PM, Sunday, 10 September 2006 Moscone Center -- Room 134, Oral
Division of Organic Chemistry |