Novel chiral hydrogen bond donor catalysts based on a 4,5-diaminoxanthene scaffold: application to enantioselective conjugate addition of 1,3-dicarbonyl compounds to nitroalkenes |
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Authors: | Tetsuhiro NemotoKazumichi Obuchi Shinji TamuraTakashi Fukuyama Yasumasa Hamada |
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Institution: | Graduate School of Pharmaceutical Sciences, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan |
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Abstract: | Novel chiral hydrogen bond donor catalysts based on a 4,5-diamino-9,9′-dimethylxanthene skeleton were designed and synthesized. Among the phenylurea-amide hybrid molecules prepared from various natural/unnatural chiral amino acids, the phenylalanine-derived catalyst, and the proline-derived catalyst were successfully applied to enantioselective conjugate addition of 1,3-dicarbonyl compounds to nitroalkenes. Using 2-acetylcyclopentanone and 2-methoxycarbonylcyclopentanone as prochiral nucleophiles, asymmetric conjugate addition to β-aryl nitroalkenes proceeded with good diastereoselectivity to provide the corresponding products bearing an all-carbon quaternary stereocenter in excellent yield with up to 95% ee. |
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Keywords: | Asymmetric synthesis Bifunctional catalyst Conjugate addition Hydrogen bond donor catalyst Organocatalyst Xanthene scaffold |
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