Synthesis of Functionalized Pentalenes via Carbonyl-Ene Reaction and Enzymatic Kinetic Resolution
作者:Sabine Laschat、Timo Anderl、Marc Emo、Angelika Baro、Wolfgang Frey
DOI:10.1055/s-2008-1067012
日期:2008.5
The synthesis of functionalized pentalene derivatives is described. Bicyclo[3.3.0]octane-3,7-dione 5 (Weiss diketone) was converted in six steps into the silyl-protected 3-methylbicyclo[3.3.0]octenol 6, which was submitted to Lewis acid catalyzed carbonyl-ene reactions with trioxane yielding the primary alcohol 7 with exocyclic double bond in high yield. By subsequent kinetic resolution with lipases compound 7 was enantiomerically enriched (up to 94% ee). It was also demonstrated that compound 7 could be functionalized by hydroboration and oxidative workup to give the trihydroxy pentalene 8 as well as by chain extension to the pentalene 23.
描述了功能化五烯衍生物的合成。通过六步反应,将双环[3.3.0]辛烯-3,7-二酮 5(Weiss 二酮)转化为硅基保护的3-甲基双环[3.3.0]辛烯醇 6,该化合物经过路易斯酸催化的羰基-烯反应与三氧烷反应,产出了高产率的含有外环双键的一级醇 7。随后,通过与脂肪酶的动力学分离,使化合物 7 的对映体富集(最高可达 94% ee)。还证明化合物 7 可以通过氢硼化和氧化处理功能化,生成三羟基五烯 8,或通过链延伸反应生成五烯 23。