Pulido Francisco J, Barbero Asunción
Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid, Spain.
Nat Protoc. 2006;1(4):2068-74. doi: 10.1038/nprot.2006.321.
A procedure for the stereoselective synthesis of substituted alkenes from alpha-silyl aldehydes, via the Peterson reaction, is described. The protocol for the preparation of alpha-silyl aldehydes is also included. Organometallic addition to the alpha-silyl aldehyde gives erythro-beta-hydroxysilanes in high yields (85-90%), which undergo elimination on treatment with potassium hydride (KH) or boron trifluoride to afford respectively Z- o E-alkenes (87-90%). The method described has been carried out using alpha-silyl aldehydes bearing the tert-butyldiphenylsilyl group. This bulky group increases the stability of the silyl aldehyde, enhances the stereoselectivity of the formation of the beta-hydroxysilanes and favors the stereocontrol of the elimination step, thus providing high yields of stereo-defined alkenes. Here we describe a two-step protocol for the synthesis of Z-1-phenyl-1-hexene from 2-tert-butyldiphenylsilyl-2-phenylethanal and n-butyllithium, followed by elimination of the resulting (1S*,2R*)-1-tert-butyldiphenylsilyl-1-phenylhexan-2-ol with KH. The total time for the synthesis, purification and isolation of the alkene is 2 days.
描述了一种通过彼得森反应从α-硅烷基醛立体选择性合成取代烯烃的方法。还包括制备α-硅烷基醛的方案。向α-硅烷基醛中进行有机金属加成反应可高产率（85 - 90%）得到赤藓型β-羟基硅烷，用氢化钾（KH）或三氟化硼处理时，这些β-羟基硅烷会发生消除反应，分别得到Z-或E-烯烃（87 - 90%）。所描述的方法是使用带有叔丁基二苯基硅基的α-硅烷基醛进行的。这个庞大的基团增加了硅烷基醛的稳定性，提高了β-羟基硅烷形成的立体选择性，并有利于消除步骤的立体控制，从而提供高产率的立体定义烯烃。在此，我们描述了一种从2-叔丁基二苯基硅基-2-苯乙醛和正丁基锂合成Z-1-苯基-1-己烯的两步方案，随后用KH消除所得的(1S*,2R*)-1-叔丁基二苯基硅基-1-苯基己烷-2-醇。烯烃的合成、纯化和分离总时间为2天。
