Cyclizations of enynes catalyzed by PtCl2 or other transition metal chlorides:: Divergent reaction pathways
Cyclizations of enynes catalyzed by PtCl2 or other transition metal chlorides:: Divergent reaction pathways
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DOI：
10.1021/ja0112184
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发表时间：
2001-10-31
影响因子：
15
通讯作者：
Echavarren, AM
中科院分区：
文献类型：
--
作者：
Méndez, M;Muñoz, MP;Echavarren, AM
1-烯-6-炔在PtCl 2催化下与醇或水反应生成侧链带有烷氧基或羟基官能团的碳环。该反应通过烯烃对（η（2-）炔）铂络合物的抗攻击而进行。C-C键和C-O键的形成通过衍生自炔的亲电试剂和亲核试剂与烯炔的双键的反式加成而立体选择性地发生。5-或6-元碳环或杂环的形成可以由1-烯-6-炔获得，这取决于烯烃上或系链处的取代基。虽然范围更有限，但Ru（II）和Au（III）氯化物也引起烯炔的烷氧基或羟基环化。基于密度泛函理论（DFT）计算，发现环丙基铂卡宾配合物是该过程中的关键中间体。在极性非亲核溶剂存在下，1-烯-6-炔在PtCl_2催化下发生环异构化反应。铂环戊烯中间体的形成得到DFT计算的支持。该反应通过反式烯丙基取代基的选择性夺氢而发生。用RuCl_3或Ru（AsPh_3）（4）Cl-_2在甲醇中可使含二取代烯烃的烯炔环化异构化。
1-En-6-ynes react with alcohols or water in the presence of PtCl2 as catalyst to give carbocycles with alkoxy or hydroxy functional groups at the side chain. The reaction proceeds by anti attack of the alkene onto the (eta (2-)alkyne)platinum complex. The formation of the C-C and C-O bonds takes place stereoselectively by trans addition of the electrophile derived from the alkyne and the nucleophile to the double bond of the enyne. Formation of five- or six-membered carbo- or heterocycles could be obtained from 1-en-6-ynes depending on the substituents on the alkene or at the tether. Although more limited in scope, Ru(II) and Au(III) chlorides also give rise to alkoxy- or hydroxycyclization of enynes. On the basis of density functional theory (DFT) calculations, a cyclopropyl platinacarbene complex was found as the key intermediate in the process. In the presence of polar, nonnucleophilic solvents, 1-en-6-ynes are cycloisomerized with PtCl2 as catalyst. Formation of a platinacyclopentene intermediate is supported by DFT calculations. The reaction takes place by selective hydrogen abstraction of the trans-allylic substituent. Cycloisomerization of enynes containing disubstituted alkenes could be carried out using RuCl3 or Ru(AsPh3)(4)Cl-2 in MeOH.