Gold-Catalyzed Intermolecular [4+2] and [2+2+2] Cycloadditions of Ynamides with Alkenes
Gold-Catalyzed Intermolecular [4+2] and [2+2+2] Cycloadditions of Ynamides with Alkenes
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DOI：
10.1002/anie.201105921
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发表时间：
2012-01-01
影响因子：
16.6
通讯作者：
Liu, Rai-Shung
中科院分区：
文献类型：
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作者：
Dateer, Ramesh B.;Shaibu, Balagopal S.;Liu, Rai-Shung
金催化的1，5-和1，6-烯炔环异构化反应代表了现代催化的重要进展。[1]这些反应提供了不寻常的和不同的碳环化合物，这些化合物不容易通过普通方法合成。重要的是，这种环异构化允许容易地获得天然存在的化合物。[2，3]由于金催化的烯炔环异构化反应仅在分子内条件下发生，因此很少有人致力于研究炔和烯之间的分子间反应。[4，5] Hashmi等人研究了苯乙炔与过量2，5-呋喃的金催化反应，该反应以低收率得到所需的2-苯基-3，5-二甲基苯酚（方案1）。[4]最近，Echavarren及其同事报道了通过苯乙炔与烯烃的金催化的分子间[2+ 2]环加成有效合成环丁烯衍生物。[5]炔烃与烯烃的分子间反应也可以用镍和钴络合物进行，得到无环丁烯或丁二烯衍生物。[6，7]我们研究了金配合物催化的炔与烯的新分子间反应。在此，我们报道了2-芳酰亚胺与烯烃的[4+ 2]环加成反应，以及芳酰亚胺与烯醇醚的[2+ 2+ 2]环加成反应（方案1）。据我们所知，对于这种类型的[2+ 2+ 2]环加成没有类似的分子间或分子内反应。[7]近年来，人们对炔醚和炔醚的亲电活化产生了很大的兴趣。研究这样的底物是因为它们比其他更常见的炔烃在金化合物催化的反应中更亲电。[8-10]这些效应源于底物-催化剂络合物的极化π炔特征（I，其也可以被绘制为烯酮共振结构（II），方案2），并且可以控制反应的区域选择性。
Gold-catalyzed cycloisomerizations of 1, 5-and 1, 6-enynes represent important advances in modern catalysis.[1] These reactions provide unusual and diverse carbocyclic compounds that are not readily synthesized by common methods. Importantly, such cycloisomerizations allow facile access to naturally occurring compounds.[2, 3] As gold-catalyzed enyne cycloisomerizations occur exclusively under intramolecular conditions, little effort has been devoted to the study of intermolecular reactions between alkynes and alkenes.[4, 5] Hashmi et al. studied the gold-catalyzed reaction of phenylacetylene with excess 2, 5-furan, which gave the desired 2-phenyl-3, 5-dimethylphenol in a low yield (Scheme 1).[4] Very recently, Echavarren and co-workers reported the efficient synthesis of cyclobutene derivatives by gold-catalyzed intermolecular [2+ 2] cycloadditions of phenylacetylenes with alkenes.[5] Intermolecular reactions of alkynes with alkenes can also be performed with nickel and cobalt complexes to give acyclic butene or butadiene derivatives.[6, 7] We investigated new intermolecular reactions of alkynes with alkenes catalyzed by gold complexes. Herein, we report [4+ 2] cycloadditions of 2-arylynamides with alkenes, and [2+ 2+ 2] cycloadditions of arylynamides with enol ethers (Scheme 1). To our knowledge, there are no analogous inter-or intramolecular reactions for this type of [2+ 2+ 2] cycloaddition.[7] Recently, there has been considerable interest in the electrophilic activation of ynamides and alkynyl ethers. Such substrates are studied because they are more electrophilic than other, more common alkynes in reactions catalyzed by gold compounds.[8–10] These effects arise from the polarized πalkyne character of the substrate–catalyst complex (I, which can also be drawn as the ketene resonance structure (II), Scheme 2) and can control the regioselectivity of reactions.