化学学报 ›› 2019, Vol. 77 ›› Issue (9): 841-849.DOI: 10.6023/A19050183 上一篇    下一篇

所属专题: 有机自由基化学

综述

可见光催化的氮自由基导向远程sp 3碳氢官能团化反应

肖丽a*(), 李嘉恒b, 王挺b*()   

  1. aBiogen, 115 Broadway, Cambridge, Massachusetts 02142, United States
    bDepartment of Chemistry, University at Albany, State University of New York, 1400 Washington Avenue, Albany, New York 12222, United States
  • 收稿日期:2019-05-15 出版日期:2019-09-15 发布日期:2019-08-14
  • 通讯作者: 肖丽,王挺 E-mail:xiao.221@buckeyemail.osu.edu;twang3@albany.edu
  • 作者简介:肖丽, 2008~2012年就读于武汉大学化学与分子科学学院; 2012~2017年就读于俄亥俄州立大学化学与生物化学学院有机化学专业(2017年获得博士学位, 导师: Craig Forsyth教授); 2018年至今在美国Biogen生物制药公司从事神经领域药物合成与工艺相关研究工作.|李嘉恒, 1988年出生于吉林省吉林市. 2012年毕业于吉林大学化学学院后在东北师范大学(NENU)王芒教授指导下开展有机氟化学研究, 并于2017年获得理学博士学位. 毕业后就职于吉林大学第一医院表观遗传医药研究所从事新药研发. 2018年8月加入纽约州立大学-奥尔巴尼分校(SUNY-Albany)王挺课题组进行博士后研究, 目前主要围绕新型有机光催化剂的合成及其应用开展相关研究工作.|王挺, 2001~2005年就读于天津大学药物科学与技术学院, 2011年在俄亥俄州立大学获博士学位. 2011至2015年在斯隆-凯特琳癌症研究中心从事博士后工作. 2015年9月加入纽约州立大学-奥尔巴尼分校(SUNY-Albany)化学系. 目前主要研究领域: 有机光催化合成方法学的研究, 以及运用新的光催化方法构建有生物活性的小分子天然产物, 糖类化合物, 多肽和糖肽化合物.

Visible-Light-Induced N-Radical Directed Remote Functionalization of sp 3 C-H Bonds

Xiao, Lia*(), Li, Jiahengb, Wang, Tingb*()   

  1. a Biogen, 115 Broadway, Cambridge, Massachusetts 02142, United States
    b Department of Chemistry, University at Albany, State University of New York, 1400 Washington Avenue, Albany, New York 12222, United States
  • Received:2019-05-15 Online:2019-09-15 Published:2019-08-14
  • Contact: Xiao, Li,Wang, Ting E-mail:xiao.221@buckeyemail.osu.edu;twang3@albany.edu

远程sp 3碳氢键官能团化反应近年来引起广泛关注, 可见光催化的氮自由基导向选择性官能化这一技术的出现使得该领域的发展取得了可喜的进展. 该策略以氮自由基介导的Hoffman-L?ffler-Freytag (HLF)反应为基础, 通过在可见光照射下激发态自由基的生成和1,5-攫取氢原子(1,5-HAT)过程, 利用反应过程中形成的自由基中间体, 实现对远程sp 3碳-氢键的修饰. 本综述就可见光催化的氮自由基导向远程碳氢官能团化反应近年来取得的进展进行简要总结.

关键词: 可见光, 自由基, 远程官能团化

The selective functionalization of unactivated sp 3 carbon-hydrogen (C—H) bond is an attractive strategy in modern organic transformation. The hydrogen atom transfer (HAT) catalysis has recently shown its advances in remotely selective activation of an inert C—H bond with great functional group compatibility, generating new carbon-carbon (C—C) bonds and carbon-heteroatom (C—O, C—N, C—X) bonds. Therefore, the remote sp 3 C—H functionalization has become an intensively investigated research area, drawing extensive attention in synthetic community. Particularly, the 1,5-hydrogen atom abstraction of nitrogen radicals, the key step of the Hoffman-L?ffler-Freytag (HLF) reaction, has been widely applied in the preparation of heterocycles. Comparing to the well-studied area of nucleophilic N-species, N-centered radical based reactions are still underdeveloped. The limited utility is partially due to the required use of hazardous radical initiators, elevated temperatures, or high-energy UV irradiation for the generation of N-radicals. Recently, visible-light photoredox catalysis has been leading efficient accesses to Nitrogen-radicals under mild conditions. The visible-light-induced nitrogen radical formation has also stimulated the development of the remote sp 3 C—H functionalization by photoredox catalysis. The classic HLF reaction requires pre-functionalization at N-center in the substrate to promote the formation of N-radical. Recently, a direct N—H single electron transfer (SET) oxidation was realized by photoredox catalysis in Knowles and Rovis’s group, generating N-radicals efficiently. The processes significantly simplified the preparation of the HLF reaction substrates and broaden the application of this classic reaction. In addition, the visible-light-induced nitrogen radical-directed reaction on modified imines provided possibilities for the remote sp 3 C—H functionalization of ketones, as ketone is the product of imine hydrolysis. Moreover, the application of chiral Lewis acid catalysis combined with visible-light photoredox catalysis enabled the asymmetric alkylation of the unactivated remote sp 3 C—H position, which achieves both regioselective and stereoselective functionalization. In conclusion, this strategy takes advantage of mild generation of N-radicals upon visible-light excitation. Subsequent 1,5-hydrogen atom transfer (1,5-HAT) and intermolecular radical coupling would realize the remote functionalization of unactivated sp 3 C—H bonds. The strategies have been successfully applied in remote C(sp 3)—H amidation, fluorination, chlorination, iodination, alkylation, vinylation, allylation, oxygenation, thioetherification, cyanation and alkynylation. In this review, we focus on visible-light-induced nitrogen radical directed functionalization of remote sp 3 C—H bonds, summarized the methodologies, and briefly reviewed their synthetic applications in pharmaceuticals and natural products.

Key words: visible-light, radical, remote functionalization