期刊
CHEMISTRY-AN ASIAN JOURNAL
卷 2, 期 1, 页码 123-134出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/asia.200600228
关键词
alkaloids; dihydropyranones; domino reactions; Michael addition; organocatalysis
Chiral quaternary ammonium phenoxides were readily prepared from commercially available cinchona alkaloids and proved to be useful new asymmetric organocatalysts. Among various chiral quaternary ammonium phenoxides, a cinch onidine-derived catalyst that bears both a sterically hindered N1-9-anthracenylmethyl group and a strongly electron withdrawing 9-O-3,5-bis(trifluoromethyl)benzyl group were found to be highly effective for the Michael addition of ketene silyl acetals (derived from phenyl carboxylates) and alpha,beta-unsaturated ketones followed by lactonization. Optically active 3,4-dihydropyran-2-one derivatives were obtained in high yields with excellent control of enantio- and diastereoselectivity. Ibis catalyst can be handled in air and stored at room temperature in a sealed bottle without decomposition for at least one month.
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