Catalytic asymmetric addition of diethylzinc to aldehydes via chiral, non-racemic β-hydroxy and β-methoxy salicylhydrazone catalysts
作者:Sucharita Banerjee、Gregory M. Ferrence、Shawn R. Hitchcock
DOI:10.1016/j.tetasy.2010.04.021
日期:2010.4
(1S,2S)-Pseudoephedrine and (1S,2S)-pseudonorephedrine have been converted to their corresponding hydrazines and condensed with either o-salicylaldehyde or 2-hydroxy-1-naphthaldehyde to afford a series of beta-hydroxysalicylhydrazones that have been employed in the asymmetric addition of diethylzinc to 2-naphthalclehyde in up to 56% ee In addition to this, the Ephedra hydrazines were also condensed with the o-hydroxyacetophenone derivative to form related hydrazones The use of these corresponding hydrazones in the asymmetric addition reaction with the diethylzinc did not yield improved enantioselectivines. Finally, Enders' hydrazine was used as a chiral scaffold for the synthesis of beta-methoxysalicylhydrazones. These compounds were employed in the asymmetric addition of diethylzinc to a variety of aromatic aldehydes with enantiomeric excesses as high as 68% ee (C) 2010 Elsevier Ltd All rights reserved
(1S,2S)-伪麻黄碱和(1S,2S)-伪去甲麻黄碱已转化为相应的肼,并与邻-水杨醛或2-羟基-1-萘醛缩合,生成一系列β-羟基水杨醛肼,这些化合物在二乙基锌与2-萘甲醛的不对称加成反应中实现了高达56%的对映体过量。此外,麻黄碱肼还与邻-羟基乙酰苯酮衍生物缩合,形成相关肼。在这些对应肼与二乙基锌进行的不对称加成反应中,并未显著提高对映选择性。最后,Enders的肼被用作手性骨架,用于合成β-甲氧基水杨醛肼。这些化合物在多种芳香醛与二乙基锌的不对称加成反应中表现出高达68%的对映体过量。
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