C−H Methylation of Iminoamido Heterocycles with Sulfur Ylides**
作者:Prithwish Ghosh、Na Yeon Kwon、Saegun Kim、Sangil Han、Suk Hun Lee、Won An、Neeraj Kumar Mishra、Soo Bong Han、In Su Kim
DOI:10.1002/anie.202010958
日期:2021.1.4
The direct methylation of N‐heterocycles is an important transformation for the advancement of pharmaceuticals, agrochemicals, functional materials, and other chemical entities. Herein, the unprecedented C(sp2)‐H methylation of iminoamido heterocycles as nucleoside base analogues is described. Notably, trimethylsulfoxonium salt was employed as a methylating agent under aqueous conditions. A wide substrate
<i>N</i>,<i>N</i>,<i>N</i>’,<i>N</i>’-Tetramethylethylenediamine-Enabled Photoredox-Catalyzed C–H Methylation of <i>N</i>-Heteroarenes
作者:Fang Liu、Zhi-Peng Ye、Yuan-Zhuo Hu、Jie Gao、Lan Zheng、Kai Chen、Hao-Yue Xiang、Xiao-Qing Chen、Hua Yang
DOI:10.1021/acs.joc.1c01325
日期:2021.9.3
Aiming at the valuable methylation process, readily available and inexpensive N,N,N′,N′-tetramethylethylenediamine (TMEDA) was first identified as a new methyl source in photoredox-catalyzed transformation in this work. By virtue of this simple methylating reagent, a facile and practical protocol for the direct C–H methylation of N-heteroarenes was developed, featuring mild reaction conditions, broad
针对有价值的甲基化过程,在这项工作中首次将易于获得且价格低廉的N , N , N' , N' -四甲基乙二胺(TMEDA) 确定为一种新的甲基化来源。凭借这种简单的甲基化试剂,开发了一种简便实用的N-杂芳烃直接 C-H 甲基化方案,具有反应条件温和、底物范围广和可扩展性等特点。机理研究表明,基本上涉及顺序光氧化还原、碱基辅助质子转移、碎裂和互变异构化过程。
Direct benzylation reactions from benzyl halides enabled by transition-metal-free photocatalysis
which are extremely challenging to be applied as radicalprecursors in visible light photocatalysis. With this transition-metal-free and oxidant-free protocol, the benzylation (or cyanomethylation) of various heterocycles including quinoxalin-2(1H)-ones, coumarin, 2-phenyl-2H-indazole, 1-methyl-5-phenylpyrazin-2(1H)-one, 1-(fluoromethyl)cinnolin-4(1H)-one, and 2,4-dibenzyl-1,2,4-triazine-3,5(2H,4H)‑dione
开发了一种使用二硫代氨基甲酸根阴离子作为催化剂的基于S N 2 的光化学策略,用于活化苄基卤化物,这在作为可见光光催化中的自由基前体应用时极具挑战性。通过这种无过渡金属和无氧化剂的方案,各种杂环的苄基化(或氰基甲基化)包括喹喔啉-2(1 H )-酮、香豆素、2-苯基-2 H-吲唑、1-甲基-5-苯基吡嗪-2(1 H )-one、1-(氟甲基)cinnolin-4(1 H )-one 和 2,4-dibenzyl-1,2,4-triazine-3,5(2 H ,4 H ) -二酮可以实现(46 个例子,高达 98% 的产率)。重要的是,一些生物学相关的 3-benzylquinoxalin-2(1 H)-也可以在温和条件下合成。
Alkylation of quinoxalin-2(1<i>H</i>)-ones using phosphonium ylides as alkylating reagents
作者:Sha Peng、Jun-Jia Liu、Luo Yang
DOI:10.1039/d1ob01858b
日期:——
through base promoted direct alkylation of quinoxalin-2(1H)-ones with phosphonium ylides as alkylating reagents under metal- and oxidant-free conditions was developed. Various 3-alkylquinoxalin-2(1H)-ones were easily obtained in good to excellent yields. Tentative mechanistic studies suggest that this reaction is likely to involve a nucleophilic addition–elimination process.
开发了一种实用且有效的方法,用于通过碱促进 quinoxalin-2(1 H )-ones 在无金属和无氧化剂条件下作为烷基化试剂直接烷基化 quinoxalin-2(1 H )-ones。各种 3-烷基喹喔啉-2(1 H )-酮很容易以良好至优异的产率获得。初步的机理研究表明,该反应可能涉及亲核加成 - 消除过程。
Site-selective and metal-free C–H nitration of biologically relevant N-heterocycles
作者:Junghyea Moon、Hyun Ku Ji、Nayoung Ko、Harin Oh、Min Seo Park、Suho Kim、Prithwish Ghosh、Neeraj Kumar Mishra、In Su Kim
DOI:10.1007/s12272-021-01351-5
日期:2021.11
The site-selective and metal-free C–Hnitration reaction of quinoxalinones and pyrazinones as biologicallyimportant N-heterocycles with t-butyl nitrite is described. A wide range of quinoxalinones were efficiently applied in this transformation, providing C7-nitrated quinoxalinones without undergoing C3-nitration. From the view of mechanistic point, the radical addition reaction exclusively occurred
描述了生物学上重要的N杂环喹喔啉酮和吡嗪酮与亚硝酸叔丁酯的位点选择性和无金属 C-H 硝化反应。多种喹喔啉酮类化合物被有效地应用于该转化中,无需进行 C3-硝化即可提供 C7-硝化喹喔啉酮类。从机理上看,自由基加成反应仅发生在缺电子N-杂环之外的富电子芳香区。这是关于喹喔啉酮在无金属条件下 C7-H 官能化的第一份报告。相反,硝化反应很容易发生在吡嗪酮类的C3位。该转化具有放大兼容性、反应条件温和和优异的官能团耐受性的特点。通过选择性还原 C7-硝化喹喔啉酮产物上的 NO 2官能团,提供苯胺衍生物,展示了所开发方法的适用性。联合机制研究有助于阐明合理的反应机制。