Palladium(0)-catalyzed synthesis of medium-sized heterocycles by using bromoallenes as an allyl dication equivalent.
Palladium(0)-catalyzed synthesis of medium-sized heterocycles by using bromoallenes as an allyl dication equivalent.
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DOI：
10.1021/ja048693x
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发表时间：
2004-06
影响因子：
15
通讯作者：
H. Ohno;H. Hamaguchi;Miyo Ohata;Shohei Kosaka;Tetsuaki Tanaka
中科院分区：
文献类型：
--
作者：
H. Ohno;H. Hamaguchi;Miyo Ohata;Shohei Kosaka;Tetsuaki Tanaka
我们已经开发了一种高度区域和立体选择性的合成含有一个或两个杂原子的中等大小的杂环，通过环化的溴联烯携带的氧，氮，或碳亲核功能在钯（0）催化剂和醇的存在下。在该反应中，溴代联烯充当烯丙基二价阳离子等价物，分子内亲核攻击仅发生在联烯部分的中心碳原子处。有趣的是，具有碳亲核试剂和五原子系链的溴联烯提供具有反式构型的八元环，而具有氧或氮亲核试剂的溴联烯选择性地提供相应的顺式环。这是第一个证明通过溴代联烯环化合成中等大小环的实施例，并且该反应提供了用于催化合成七元和八元杂环而不使用高稀释条件的非常有用的方法。
We have developed a highly regio- and stereoselective synthesis of medium-sized heterocycles containing one or two heteroatoms via cyclization of bromoallenes bearing an oxygen, nitrogen, or carbon nucleophilic functionality in the presence of a palladium(0) catalyst and alcohol. In this reaction, bromoallenes act as an allyl dication equivalent, and the intramolecular nucleophilic attack takes place exclusively at the central carbon atom of the allene moiety. Interestingly, bromoallenes having a carbon nucleophile with a five-atom tether afford eight-membered rings with trans-configuration, while those having an oxygen or a nitrogen nucleophile give the corresponding cis-rings selectively. This is the first example that demonstrates the synthesis of medium-sized rings via cyclization of bromoallenes, and this reaction provides a very useful method for a catalytic synthesis of seven- and eight-membered heterocycles without using high dilution conditions.