Highly enantioselective Diels-Alder reactions of Danishefsky type dienes with electron-deficient alkenes catalyzed by Yb(III)-BINAMIDE complexes |
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Authors: | Sudo Yukinori Shirasaki Daisuke Harada Shinji Nishida Atsushi |
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Affiliation: | Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. |
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Abstract: | 1-Methoxy-3-trimethylsiloxy-1,3-butadiene (Danishefsky's diene) is recognized as a synthetically useful diene due to its high reactivity in the Diels-Alder reaction with electron-deficient alkenes to give oxygen-functionalyzed cyclohexenes and substituted cyclohexenones, which are important building blocks for the total synthesis of natural products. However, the development of catalytic enantioselective versions of Diels-Alder reactions using Danishefsky type dienes with electron-deficient alkenes has been difficult because of the instability of the dienes under Lewis acidic conditions. Only highly reactive CO and CN double bonds are employed in a hetero-Diels-Alder reaction which proceeds under catalysis of chiral Lewis acids. We have developed a new chiral ligand, BINAMIDE, which is easily prepared from 1,1'-binaphtyl-2,2'-diamine by acylation. The highly diastereo- and enantioselective Diels-Alder reaction of Danishefsky type dienes with electron-deficient alkenes in the presence of an Yb(III)-BINAMIDE complex has been developed. The reaction proceeded in an exoselective mode and gave chiral highly functionalized cyclohexene derivatives in good yields. |
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