Synthesis of Oxacyclic Scaffolds via Dual Ruthenium Hydride/Brønsted Acid-Catalyzed Isomerization/Cyclization of Allylic Ethers
作者:Erhad Ascic、Ragnhild G. Ohm、Rico Petersen、Mette R. Hansen、Casper L. Hansen、Daniel Madsen、David Tanner、Thomas E. Nielsen
DOI:10.1002/chem.201304270
日期:2014.3.17
A ruthenium hydride/Brønsted 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 (Brønsted acid catalysis) amenable to endo cyclization
据报道,氢化钌/布朗斯台德酸催化的串联序列可用于合成1,3,4,9-四氢吡喃[3,4- b ]吲哚(THPIs)和相关的氧环骨架。该过程被设计的前提是容易得到的烯丙基醚将经历连续的异构化,第一至烯醇醚(RU催化),然后到oxocarbenium离子(布朗斯台德酸催化)适合于内 环化栓系亲核体。该方法不仅为合成THPI的传统oxa-Pictet-Spengler反应提供了有吸引力的替代方法,而且还方便地获得THPI同类物和其他重要的乙环(如乙缩醛)。