Preparation of Highly Reactive Pyridine- and Pyrimidine-Containing Diarylamine Antioxidants
Preparation of Highly Reactive Pyridine- and Pyrimidine-Containing Diarylamine Antioxidants
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DOI：
10.1021/jo301013c
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发表时间：
2012-08-17
影响因子：
3.6
通讯作者：
Pratt, Derek A.
中科院分区：
文献类型：
--
作者：
Hanthorn, Jason J.;Valgimigli, Luca;Pratt, Derek A.
我们最近报告了我们开发新型二芳胺自由基捕获抗氧化剂的初步报告(Hanthorn，J.J.等人)。J.Am化学。SoC。2012,134,8306-8309)，其中我们证明了二苯胺中的环氮化合物表现出对过氧基的H原子转移活性和对单电子氧化的稳定性之间的折衷。在此，我们提供了与该报告相关的合成努力的细节，这些努力已得到实质性扩展，以产生一个取代杂环二芳胺的库，我们已使用该库进一步深入了解这些化合物作为抗氧化剂的结构-反应关系(见所附文件，DOT：10.1021/jo301012x)。二芳胺是由2-氨基吡啶和2-氨基嘧啶以短的模块化序列合成的，其中中间体吡啶(Mi)二溴的氨化反应，然后是钯催化的胺和前体溴化物的交叉偶联反应是合成二芳胺的关键步骤。结果表明，以Pd(ETA(3)-1-PhC3H4)(ETA(5)-C5H5)为预催化剂时，交叉偶联反应进行得最好，产率高于Pd-2(Dba)(3)。
We recently reported a preliminary account of our efforts to develop novel diarylamine radical-trapping antioxidants (Hanthorn, J. J. et al. J. Am. Chem. Soc. 2012, 134, 8306-8309) wherein we demonstrated that the incorporation of ring nitrogens into diphenylamines affords compounds which display a compromise between H-atom transfer reactivity to peroxyl radicals and stability to one-electron oxidation. Herein we provide the details of the synthetic efforts associated with that report, which have been substantially expanded to produce a library of substituted heterocyclic diarylamines that we have used to provide further insight into the structure-reactivity relationships of these compounds as antioxidants (see the accompanying paper, DOT: 10.1021/jo301012x). The diarylamines were prepared in short, modular sequences from 2-aminopyridine and 2-aminopyrimidine wherein aminations of intermediate pyri(mi)dyl bromides and then Pd-catalyzed cross-coupling reactions of the amines and precursor bromides were the key steps to yield the diarylamines. The cross-coupling reactions were found to proceed best with Pd(eta(3)-1-PhC3H4)(eta(5)-C5H5) as precatalyst, which gave higher yields than the conventional Pd source, Pd-2(dba)(3).