Synthesis of Oxacyclic Scaffolds via Dual Ruthenium Hydride/Bronsted Acid-Catalyzed Isomerization/Cyclization of Allylic Ethers
Synthesis of Oxacyclic Scaffolds via Dual Ruthenium Hydride/Bronsted Acid-Catalyzed Isomerization/Cyclization of Allylic Ethers
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DOI：
10.1002/chem.201304270
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发表时间：
2014-03-17
影响因子：
4.3
通讯作者：
Nielsen, Thomas E.
中科院分区：
文献类型：
--
作者：
Ascic, Erhad;Ohm, Ragnhild G.;Nielsen, Thomas E.
报道了1，3，4，9-四氢吡喃并[3，4-b]吲哚(THPI)及其草环支架的合成。该工艺的设计前提是，容易获得的烯丙基醚将经历连续的异构化，首先是烯醇醚(Ru催化)，然后是易于与系留亲核试剂内环化的氧碳正离子(BrOnsted酸催化)。该方法不仅为合成THPI提供了一种替代传统的oxa-Pictet-Spengler反应的有吸引力的方法，而且还可以方便地获得THPI同系物和其他重要的氧杂环，如缩醛。
A ruthenium hydride/BrOnsted acid-catalyzed tandem sequence is reported for the synthesis of 1,3,4,9-tetrahydropyrano[3,4-b]indoles (THPIs) and related oxacyclic scaffolds. The process was designed on the premise that readily available allylic ethers would undergo sequential isomerization, first to enol ethers (Ru catalysis), then to oxocarbenium ions (BrOnsted acid catalysis) amenable to endocyclization with tethered nucleophiles. This methodology provides not only an attractive alternative to the traditional oxa-Pictet-Spengler reaction for the synthesis of THPIs, but also convenient access to THPI congeners and other important oxacycles such as acetals.