Sharpless不对称羟胺化

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在很多的生物学上很重要的分子中,立体β-胺基醇结构单元是关键的部分。要合成这样的分子或其衍生物,烯烃与这两种杂原子直接加成为最直接的方法。虽然20多年前就已经知道的锇或钯参与的烯烃氨基羟基反应,但是为了将这一反应发展成为催化性的不对称过程,仍存在一些问题。小组最近发现的锇参与的不对称氨基羟基化反应(AA反应),可以优异的对映选择性和极好的产率直接将这种官能团引入烯烃。


 Sharpless不对称羟胺化示例:


A 20 ml of scintillation vial equipped with a magnetic stirrer wascharged with a solution of MeSO2NclNa(455mg, 3.0mmol, 3.0 equiv) in 7.5 ml ofwater, 7.5 ml of nPrOH, and (DHQD)2PHAL (40mg, 0.05mmol, 0.05 equiv). To theresulting stirred clear colorless solution was then added isopropyltrans-cinnmate (190mg, 1.0mmol), followed by K2Os2(OH)4(14.8mg, 0.04mmol, 0.04equiv). The reaction mixture turned green after several minutes and was stirredfor 3.5 hours, by which time the reaction mixture has turned a clear, lightyellow. The presumed significance of the color change as an indication of theend point of the reaction was confirmed by a TLC analysis, which revealed thatno olefin remained. (With dimethyl fumarate the green color was only observedwhen an additional 0.5 equiv tert-butyl hypochlorite was added. For thefumarate case, the extra tert-butyl hypochlorite also resulted in much betteree and yield.) the reaction was then quenched by addition of 10 ml of saturatedNa2S3( This reductive quench is exothermic and cooling is needed forlarge-scales). The added salt caused phase separation. The aqueous phase wasseparated and extracted with ethyl acetate(3X30ml). The combined organic phaseswere dried over Mg2SO4 and concentrated to afford the crude product(impuritieswere mainly methanesulfonamide and diol). For an accurate yield the crudeproduct was purified by flash chromatography( SiO2, 30% ethyl acetate/hexane)and afforded 195mg(65%, >99%ee) crystalline aminohydroxylation product.


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相关反应介绍


2016-07-18 nf 


在锇催化下胺基和羟基对烯烃进行顺式加成,通过加入手性配体(二氢奎宁或二氢奎宁衍生物类手性配体)实现对映选择性。常见的氮源(X

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