Synthesis ofcis-Hedione® and Methyl Jasmonatevia CascadeBaylis-Hillman Reaction andClaisen Ortho Ester Rearrangement
作者:Christian Chapuis、George H. Büchi、Hans Wüest
DOI:10.1002/hlca.200590248
日期:2005.12
The exocyclically unsaturated conjugated keto esters 10, obtained via a Claisen ortho ester rearrangement of the allylic hydroxy ketones 9, were either directly hydrogenated or partially isomerized into the endocyclically unsaturated tetrasubstituted didehydrojasmonoid intermediates 14, prior to a more selective hydrogenation with Pd/C in cyclohexane to the disubstituted oxocyclopentaneacetates 15
通过烯丙基羟基酮9的克莱森原酸酯重排而获得的环外不饱和共轭酮酯10直接加氢或部分异构化成环内不饱和四取代的二氢茉莉酮中间体14,然后在环己烷中用Pd / C进行更选择性的氢化。生成二取代的氧代环戊烷乙酸酯15(方案2)。关键中间体9通过四步序列要么获得,包括从烯酮缩醛保护/脱保护1,在羟基酮的特定情况下9A(方案1),或更直接地并且通常是通过环戊-2-en-1-酮(16)和适当的醛17的Baylis-Hillman反应(方案2)。这些醛的明智选择为立体选择性引入部分顺式-或差向异构反式-C(2)茉莉酮类侧链打开了通用的修饰,而手性[1,1'-双萘] -2催化的Baylis-Hillman反应可以以一锅级联方式有效地进行1,2'-二醇(BINOLs)19(方案3),包括原酸酯克莱森重排。