| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Highly enantioselective (96% ee) and endσselective (> 99 : 1) cycloaddition reactions were observed between carbonylylides, generated from o-(p-bromobenzyloxy)carbonyl-α-diazoacetophenone, and 3-crotonoyl-2-oxazolidinone using chiral 2,6-(oxazolinyl)pyridine-Yb(OTf)_3 (20 mol%) as the chiral Lewis acid catalyst. In contrast, high exo-selectivity (exo:endo= 82:18; 96% ee, exo) was observed for the reaction o-methoxycarbonyl-α-diazoacetophenone of 3-acryloyl-2-oxazolidinone under similar conditions as reported previously. In the case of cycloaddition reactions between 2-benzopyrylium-4-olate, generated from o-methoxycarbonyl-α-diazoacetophenon, and 3-cinnamoyl-or 3-[(E)-3-ethoxylcarbonylpropenoyl]-2-oxazolidinones, using the same chiral Lewis acid, the reaction favored the endo-adduct with relatively good enantioselectivity (72% ee and 78% ee, respectively). We have also found the first successful example of reverse electron demand dipole-LUMO/dipolarophile-HOMO controlled cycloaddition
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reactions between carbonyl ylides, which were generated from o-methoxycarbonyl-α-diazoacetophenone and their acyl derivatives as precursors, and vinyl ether derivatives with high levels of asymmetric induction (97-77 %ee) using chiral 2,6-(oxazolinyl)pyridine-Eu(III) or binaphthyldiimine-Ni(II) complexes as chiral Lewis acid catalysts.
In the investigations of other 1,3-dipoles for catalytic asymmetric cycloaddition reactions, we have found the first example of high levels of asymmetric induction (97-74% ee) along with high diastereoselectivity (>99:1-64:36) in dipole-HOMO/dipolarophile-LUMO-controlled asymmetric 1,3-dipolar cycloaddition reactions between fused azomethine imines and 3-acryloyl-2-oxazolidinone using a binaphthyldiimine-Ni(II) complex as a chiral Lewis acid catalyst. Good enantioselectivities (93-54% ee) with high regioselectivities (94:6-86:14) were also obtained in the 1,3-dipolar cycloaddition reactions between aromatic nitrile oxides, which were generated in situ from the corresponding iminoyl chlorides in the presence of 4Å molecular sieves, and 3-(2-crotonoyl)-5,5-dimethyl-2-oxazolidinones when the reactions were performed in the presence of the chiral binaphthyldiimine-Ni(II) complex (30 mol%). Less
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