Bi Hong-Yan, Du Min, Pan Cheng-Xue, Xiao Yuhong, Su Gui-Fa, Mo Dong-Liang
State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry & Pharmaceutical Sciences , Guangxi Normal University , 15 Yu Cai Road , Guilin 541004 , China.
School of Chemistry and Chemical Engineering , Hunan University of Science and Technology , Xiangtan 411201 , P. R. China.
J Org Chem. 2019 Aug 16;84(16):9859-9868. doi: 10.1021/acs.joc.9b00784. Epub 2019 Aug 8.
An atom-economical and practical method for the efficient synthesis of various pyrazino[1,2-]indole-2-oxides was developed through a nickel(II)-catalyzed [5 + 1] annulation of 2-carbonyl-1-propargylindoles with hydroxylamine in water without using an organic solvent. The reaction involved an initial condensation of 2-carbonyl-1-propargylindoles with hydroxylamine to afford oxime intermediates, which then underwent a nickel(II)-catalyzed 6-exo-dig cyclization. Preliminary studies showed that (-Bu)NI served as a phase transfer catalyst and promoted the formation of active nickel(II) species. More importantly, the nickel(II) salt and phase transfer catalyst-in-water could be recycled seven times, and a gram scalable product was easily obtained in good yields through a filtration and washing protocol.
通过在水中使用镍（II）催化2-羰基-1-炔丙基吲哚与羟胺进行[5 + 1]环化反应，开发了一种原子经济且实用的方法，可高效合成各种吡嗪并[1,2 - ]吲哚-2-氧化物，无需使用有机溶剂。该反应首先涉及2-羰基-1-炔丙基吲哚与羟胺的缩合反应，生成肟中间体，然后肟中间体进行镍（II）催化的6-外向-环化反应。初步研究表明，（-Bu）NI作为相转移催化剂，促进了活性镍（II）物种的形成。更重要的是，镍（II）盐和水中的相转移催化剂可以循环使用七次，通过过滤和洗涤操作，很容易以良好的产率获得克级规模的产物。
