The squarate ester-polyquinane connection. An analysis of the capacity of achiral divinyl adducts to rearrange spontaneously to polycyclic networks housing multiple stereogenic centers
The squarate ester-polyquinane connection. An analysis of the capacity of achiral divinyl adducts to rearrange spontaneously to polycyclic networks housing multiple stereogenic centers
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DOI：
10.1021/ja963214i
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发表时间：
1997-02-12
影响因子：
15
通讯作者：
Morwick, TM
中科院分区：
文献类型：
--
作者：
Paquette, LA;Morwick, TM
方二异丙基及其相关的环丁烯-1,2-二酮与2个相等的烯基阴离子或2个不同的烯基阴离子各1个相等的缩合反应是一种高度窄控合成二、三、四醌的有效方法。两个反应级联已被确定，最普遍的和经常排他的反应过程是由两个亲核试剂的反式1,2加成引发的。两个连续的控制过程随后产生一个双电荷的八元环中间体，其质子化导致跨环雾化。第二种选择是从顺式1,2加成开始的，这一事件通过二阴离子氧- cope重排触发结构重组。当烯基阴离子被充分取代时，这两种途径在立体化学上是可区分的，一种由反式1,4加成组成的次要途径在某些情况下起作用，特别是当烯基锂是“软”的时候。乙基阴离子也可以成功地利用；在这种情况下，区域控制质子化的好处表面，并产生一个单一的产物，这些复杂的串联反应的其他方面已经研究和讨论。
The condensation of diisopropyl squarate and related cyclobutene-1,2-diones with 2 equiv of the same alkenyl anion or 1 equiv each of two different alkenyl anions can be a very effective method for the highly stenocontrolled synthesis of di-, tri-, and tetraquinanes. Two reaction cascades have been identified, The most prevalent and often exclusive reaction course is triggered by trans 1,2-addition of the two nucleophiles. Two consecutive conrotatory processes subsequently arise to deliver a doubly charged eight-membered ring intermediate, protonation of which leads to transannular adolization. The second option begins with cis 1,2-addition, this event triggering structural reorganization via a dianionic oxy-Cope rearrangement, When the alkenyl anions are sufficiently substituted, the two pathways are distinguishable on stereochemical grounds, A minor pathway consisting of trans 1,4-addition is seen to operate in certain contexts, especially when the alkenyllithium is ''soft''. Acetylide anions can also be utilized successfully; in such cases, the benefit of regiocontrolled protonation surfaces and gives rise to a single product, Other aspects of these complex tandem reactions have been investigated and are discussed.