4-Alkoxycarbonyl- and Aminocarbonyl-Substituted Isoxazoles as Masked Acrylates and Acrylamides in the Asymmetric Synthesis of Δ<sup>2</sup>-Isoxazolines
作者:Connie K. Y. Lee、Anthony J. Herlt、Gregory W. Simpson、Anthony C. Willis、Christopher J. Easton
DOI:10.1021/jo0602569
日期:2006.4.1
treatment with sodium borohydride and sodium trifluoroacetoxyborohydride, respectively. They are also alkylated at C5 through sonication with secondary and tertiary alkyl iodides in the presence of zinc dust and copper(I) iodide. These reactions are analogous to those observed with acrylates and acrylamides. The behavior is characteristic of the 4-substituted isoxazoles but not the 5-substituted regioisomers
4-烷氧基羰基和氨基羰基取代的异恶唑经历共轭还原,得到Δ 2上分别与硼氢化钠和三氟乙酰氧基钠,治疗-isoxazolines。它们还通过在锌粉和碘化铜(I)存在下,通过仲和叔烷基碘的超声处理在C5烷基化。这些反应类似于用丙烯酸酯和丙烯酰胺观察到的反应。该行为是4-取代的异恶唑的特征,而不是5-取代的区域异构体的特征。4,5-二取代异恶唑的还原反应和4-取代异恶唑的C5烷基化反应通常可提供反式-4,5-二取代的异恶唑啉。将手性助剂并入烷氧羰基中可保持这种相对的立体选择性。它在还原中没有提供显着水平的不对称诱导,但是烷基化在C4和C5处都以良好的立体控制水平发生。由于两种助剂的对映异构体均可用,因此可以以93至≥98%de的比例获得产品的任何一种对映异构体。该方法,因此,提供了一种互补的方法来氧化腈环加成到烯烃为Δ的不对称合成2 -isoxazolines。