Dienolates of Cycloalkenones and α,β‐Unsaturated Esters Form Diels–Alder Adducts by a Michael/Michael‐Tandem Reaction Rather Than in One Step
作者:Ann‐Christine Loesche、Reinhard Brückner
DOI:10.1002/ejoc.201801193
日期:2019.1.23
lithium enolates by anionic Diels–Alder reactions. However, in principle, the respective products might form not only in a single step but also in two consecutive – or “tandem” – Michael additions, the first of which occurs intermolecularly, the second intramolecularly. Three cyclic lithium dienolates and four esters with a stereogenic Cα=Cβ bond reacted to give Diels–Alder adducts (10 times) or failed to
已知α,β-不饱和酯和1,3-二烯-2-醇锂通过阴离子Diels-Alder反应提供双环烯醇锂。但是,原则上,各自的产物不仅可以一步一步形成,而且可以连续两次(或“串联”)迈克尔加成形成,其中第一种在分子间发生,第二种在分子内发生。三个环状锂dienolates和四个酯与立体异构源ç α = C β键反应生成狄尔斯-阿尔德加合物(10次)或未反应(2次)。七个反应性组合提供了加合物,其中前一酯部分的构型部分被反转。这排除了一致的途径作为其起源。这是令人惊讶的,因为1,3-二烯的C-2的供体以烷基<芳基<烷氧基≈三烷基甲硅烷氧基<酰氨基的顺序加速了正常的电子需求Diels-Alder反应。李⊕ Ø ⊖是一个更好的捐赠者仍然,为什么机构是不可一致,而不是一致(和更异步)不是很明显。