Water-Assisted Nitrile Oxide Cycloadditions: Synthesis of Isoxazoles and Stereoselective Syntheses of Isoxazolines and 1,2,4-Oxadiazoles
作者:Chatchai Kesornpun、Thammarat Aree、Chulabhorn Mahidol、Somsak Ruchirawat、Prasat Kittakoop
DOI:10.1002/anie.201511730
日期:2016.3.14
Conventional methods generate nitrile oxides from oxime halides in organic solvents under basic conditions. However, the present work revealed that water‐assisted generation of nitrile oxides proceeds under mild acidic conditions (pH 4–5). Cycloadditions of nitrile oxides with alkynes and alkenes easily occurred in water without using catalysts, thus yielding isoxazoles and isoxazolines, respectively
常规方法是在碱性条件下由有机溶剂中的肟卤化物生成腈氧化物。但是,目前的工作表明,在弱酸性条件下(pH值为4-5)会进行水辅助生成的腈氧化物。在不使用催化剂的情况下,腈类化合物与炔烃和烯烃的环加成反应很容易在水中发生,因此分别制得异恶唑和异恶唑啉,对五元和六元环状烯烃具有出色的立体选择性。还实现了两个单元的腈与环己烯的双立体选择性环加成反应,从而得到具有独特的异恶唑啉-恶二唑骨架的1,2,4-恶二唑衍生物。从具有环应变的单萜制备对映体纯的异恶唑啉。在一种情况下,仅制备了蝴蝶状结构的异恶唑啉,