AsymmetricDiels-Alder Reactions of Neopentyl-Ether-Shielded Acrylates and Allenic Esters: Syntheses of (?)-Norbornenone and (?)-?-Santalene
作者:Wolfgang Oppolzer、Christian Chapuis、Dominique Dupuis、Maodao Guo
DOI:10.1002/hlca.19850680803
日期:1985.12.18
Starting from (+)- or (−)-camphor, the antipodal alcohols 14 and 18, respectively, have been prepared; the corresponding acrylates 15 and 19 underwent TiCl2(i-PrO)2-mediated Diels-Alder additions to cyclopentadiene to give adducts 20a and 22a respectively, with 95 % endo- and 99.2% πpH-face selectivities. Adduct 22a was converted to enantiomerically pure norbornenone 26. Addition of 1,3-butadiene to
从(+)-或(-)-樟脑开始,分别制备了对映体醇14和18。相应的丙烯酸酯15和19经历TiCl 2(i-PrO)2介导的Diels - Alder加成到环戊二烯中,分别得到加合物20a和22a,其内表面选择性和95 %πpH选择性。加合物22a被转化为对映体纯的降冰片烯酮26。在TiCl 4存在下将1,3-丁二烯添加到丙烯酸酯15中得到具有> 95.6%的立体分化的3-环己烯基羧酸盐29。TiCl 2(i-PrO)2促进的环戊二烯与烯丙基酯43的[4 + 2]环加成反应,并进行了99%的表面分化,是有效(-)-β-檀香烯((- )-41)同时回收手性对照醇14。