催化学报 ›› 2018, Vol. 39 ›› Issue (3): 487-494.DOI: 10.1016/S1872-2067(17)62896-1

• 论文 • 上一篇    下一篇

可见光催化醛、酮或亚胺与缺电子芳烃还原偶联构筑芳基取代醇和胺

刘赞a,b, 南小磊a,b, 雷涛a,b, 周超a,b, 王阳a,b, 刘文强a,b, 陈彬a,b, 佟振合a,b, 吴骊珠a,b   

  1. a 中国科学院理化技术研究所, 光化学转换与功能材料重点实验室, 北京 100190;
    b 中国科学院大学, 北京 100049
  • 收稿日期:2017-09-17 修回日期:2017-10-26 出版日期:2018-03-18 发布日期:2018-03-10
  • 通讯作者: 吴骊珠
  • 基金资助:

    国家科技部基金(2013CB834804,2014CB239402);国家自然科学基金(21390404,91427303);中国科学院战略先导研究项目基金(XDB17030400).

Photo-induced reductive cross-coupling of aldehydes, ketones and imines with electron-deficient arenes to construct aryl substituted alcohols and amines

Zan Liua,b, Xiaolei Nana,b, Tao Leia,b, Chao Zhoua,b, Yang Wanga,b, Wenqiang Liua,b, Bin Chena,b, Chenho Tunga,b, Lizhu Wua,b   

  1. a Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China;
    b University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-09-17 Revised:2017-10-26 Online:2018-03-18 Published:2018-03-10
  • Contact: 10.1016/S1872-2067(17)62896-1
  • Supported by:

    This work was supported by the Ministry of Science and Technology of China (2013CB834804, 2014CB239402), the National Natural Science Foundation of China (21390404, 91427303), and the Strategic Priority Research Program of the Chinese Academy of Science (XDB17030400).

摘要:

通过C=X(X=O,N)双键极性翻转构筑碳-碳键是有机化学反应的重要合成策略.传统C=X(X=O,N)双键的极性翻转往往需要苛刻的反应条件和对水或空气敏感的强还原剂辅助,导致其适用范围受限.近年来,可见光催化反应以其独特高效的单电子转移特性,在室温条件下实现了这一类贫电子官能团向亲核性中间体的高效转化.该策略已经拓展C=X(X=O,N)双键自身或与烷基链的偶联,从而得到烷基取代的醇和胺类化合物.本文利用可见光催化反应使C=X(X=O,N)双键极性翻转与芳香化合物的直接偶联,高效温和地合成芳基取代的醇和胺.反应无需强还原剂,底物适用范围广.该方法是对可见光催化C=X(X=O,N)双键极性翻转的重要补充,具有潜在的应用价值.
本文以苯甲醛和1,4-二氰基苯为底物,fac-Ir(ppy)3为光敏剂,二异丙基乙胺为终端还原剂,DMSO为溶剂,蓝光照射12h能够以82%的收率实现模板反应.其它光敏剂如[Ru(bpy)3]Cl2则不能催化该反应.溶剂效应指出,丙酮、乙腈可以得到低于40%的收率,甲醇、二氯甲烷、DMF等溶剂不适用该反应体系.控制实验证实,光敏剂、二异丙基乙胺和光照三个反应组分缺一不可.底物拓展发现,不同取代基的芳基腈类化合物包括烷基取代、砜基和酯基取代甚至杂芳环取代都能很好地适用于该体系,芳基醛、酮以及亚胺作为反应的另一组分亦能高效参与该还原偶联反应.
自由基捕获实验证实反应过程中涉及自由基历程.光谱淬灭实验表明,芳香腈是唯一有效淬灭激发态fac-Ir(ppy)3发光的物种.进一步结合底物的氧化还原电位,证实芳香腈能被激发态的光敏剂fac-Ir(ppy)3还原,但二异丙基乙胺和芳香醛、酮不能与激发态光敏剂发生作用,催化反应经历光敏剂的氧化淬灭路径.首先,光敏剂受光激发到达激发态,与芳基腈发生单电子转移.随后,二异丙基乙胺促使失去电子的铱配合物还原再生,得到相应氮自由基阳离子.该氮自由基阳离子活化反应体系中的C=X(X=O,N)双键,使其从激发态铱物种得到电子形成苄位自由基,进而与得到电子的芳基氰偶联得到最终产物.

关键词: 芳基取代的醇和胺, 还原偶联, 极性翻转, 光催化, 芳基化

Abstract:

Umpolung reactions of C=X bonds (X=O, N) are valuable ways of constructing new C-C bonds, which are sometimes difficult to be constructed using traditional synthetic pathways. Classical polarity inversion of C=X bonds (X=O, N) usually requires air or moisture-sensitive and strong reducing agents, which limit the feasibility of substrate scope. Herein we describe a photo-induced reductive cross-coupling reaction of aldehydes, ketones and imines with electron-deficient arenes (aromatic nitriles) using fac-Ir(ppy)3 as a photocatalyst and diisopropylethylamine (DIPEA) as a terminal reductant under visible light irradiation. Mild conditions and high yields mean that this new polarity inversion strategy can be used with aryl-substituted alcohols and amines. Spectroscopic studies and control experiments have demonstrated the oxidative quenching of Ir(ppy)3* by electron-deficient arenes involved in the key step for the C-C bond formation.

Key words: Aryl substituted alcohols and amines, Radical-radical cross coupling, Polarity reversal, Photocatalysis, Arylation