Platinum- and gold-catalyzed cycloisomerization reactions of hydroxylated enynes
Platinum- and gold-catalyzed cycloisomerization reactions of hydroxylated enynes
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DOI：
10.1021/ja048094q
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发表时间：
2004-07-21
影响因子：
15
通讯作者：
Fürstner, A
中科院分区：
文献类型：
--
作者：
Mamane, V;Gress, T;Fürstner, A
在催化量的PtCl2或(PPh_3)AuCl/AgSbF_6作用下，烯炔在其中一个丙叉位置上含有羟基，导致选择性重排，生成双环[3.1.0]己烷-3-酮衍生物。用烯丙基氯二甲基硅烷(4)和PtCl2通过反应级联反应得到相同的产物，该反应级联反应包括初始铂催化的烯丙化反应，然后原位生成的高烯丙醇的环异构化。这一新的骨架重组过程被实施为萜类化合物萨宾酮(18)和萨宾醇(19)的简明全合成。此外，研究还表明，羟基化的烯炔转化为相应的乙酸酯，然后与由(PPh3)AuCl和AgSbF6形成的阳离子金催化剂反应，在双环[3.1.0]己烷骨架的C-2位上打开了含酮功能的异构体的入口。氚标记实验的结果和环异构化反应立体化学过程的分析与环丙基甲基铂卡宾作为反应中间体的形成是一致的。
Exposure of enynes containing a hydroxyl group at one of the propargylic positions to catalytic amounts of either PtCl2or (PPh3)AuCl/AgSbF6results in a selective rearrangement with formation of bicyclo[3.1.0]hexan-3-one derivatives. The same products are obtained by a “one-pot” process on treatment of an alkynal with allylchlorodimethylsilane (4) and PtCl2via a reaction cascade involving an initial platinum-catalyzed allylation followed by the cycloisomerization of the homoallylic alcohol formed in situ. This novel skeletal reorganization process was implemented into a concise total synthesis of the terpenes sabinone (18) and sabinol (19). Furthermore it is shown that conversion of the hydroxylated enynes into the corresponding acetates followed by reaction with a cationic gold catalyst formed from (PPh3)AuCl and AgSbF6opens entry into isomeric products bearing the ketone function at the C-2 position of the bicyclo[3.1.0]hexane skeleton. The outcome of a deuterium labeling experiment and the analysis of the stereochemical course of the cycloisomerization reaction are consistent with the formation of cyclopropylmethyl platinum carbene species as reactive intermediates.