Fischer-type indolization of N-aryl-C-cyclopropyl hydrazones generated in situ followed by chemoselective reduction using tert-butyl iodide as an anhydrous HI generator was developed. This protocol provides indoles bearing carboxylic acid derivative units. A series of control experiments indicated the HI-mediated formation and reduction of spirocyclopropyl indolenines. Anhydrous HI functions as a Brønsted
开发了原位产生的N-芳基-C-环丙基腙的 Fischer 型吲哚化,然后使用叔丁基碘作为无水 HI 发生器进行化学选择性还原。该协议提供了带有羧酸衍生物单元的吲哚。一系列对照实验表明 HI 介导的螺环丙基二氢吲哚的形成和还原。无水 HI 可作为布朗斯台德酸和还原剂,促进不稳定反应中间体和碘化混合物在平衡状态下的成功转化。
Temporary Generation of a Cyclopropyl Oxocarbenium Ion Enables Highly Diastereoselective Donor-Acceptor Cyclopropane Cycloaddition
作者:Juliette Sabbatani、Nuno Maulide
DOI:10.1002/anie.201601340
日期:2016.6.1
tetrahydrofurans display three new chiral centers formed with highly diastereoselectivity. This method is stereocomplementary to most previously reported cycloadditions of malonate diesters, relies on the transient generation of cyclopropyl oxocarbenium ions, proceeds under mild conditions, and is based on the concept of temporary activation of an otherwise inert protecting group.