Catalytic Synthesis of N-Heterocycles via Direct C(sp(3))-H Amination Using an Air-Stable Iron(III) Species with a Redox-Active Ligand.
Catalytic Synthesis of N-Heterocycles via Direct C(sp(3))-H Amination Using an Air-Stable Iron(III) Species with a Redox-Active Ligand.
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DOI：
10.1021/jacs.7b00270
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发表时间：
2017-04-12
影响因子：
15
通讯作者：
van der Vlugt JI
中科院分区：
文献类型：
--
作者：
Bagh B;Broere DLJ;Sinha V;Kuijpers PF;van Leest NP;de Bruin B;Demeshko S;Siegler MA;van der Vlugt JI
FeCl3与氧化还原活性吡啶-氨基苯酚配体NNOH2在碱存在下和有氧条件下配位生成FeCl2（NNOISQ）（1），其特征在于高自旋FeIII和NNOISQ自由基配体。从实验和计算数据推断，该复合物具有整体S = 2自旋状态。配体为中心的自由基与Fe中心反铁磁耦合。容易获得的、明确定义的和空气稳定的1催化未活化的有机叠氮化物的具有挑战性的分子内直接C（sp3）-H胺化，以产生一系列饱和的N-杂环，其具有迄今报道的最高转换数（TON）（1摩尔%的1，12小时，TON = 62; 0.1摩尔%的1，7天，TON = 620）。该催化剂易于再循环，催化活性无明显损失。对1-叠氮基-4-苯基丁烷（S1）的C（sp3）-H胺化反应进行了详细的动力学研究，结果表明叠氮底物为零级反应，催化剂和Boc2O均为一级反应。一个阳离子铁络合物，从中性预催化剂与Boc2O反应后产生的，建议作为催化活性物种。
Coordination of FeCl3 to the redox-active pyridine–aminophenol ligand NNOH2 in the presence of base and under aerobic conditions generates FeCl2(NNOISQ) (1), featuring high-spin FeIII and an NNOISQ radical ligand. The complex has an overall S = 2 spin state, as deduced from experimental and computational data. The ligand-centered radical couples antiferromagnetically with the Fe center. Readily available, well-defined, and air-stable 1 catalyzes the challenging intramolecular direct C(sp3)–H amination of unactivated organic azides to generate a range of saturated N-heterocycles with the highest turnover number (TON) (1 mol% of 1, 12 h, TON = 62; 0.1 mol% of 1, 7 days, TON = 620) reported to date. The catalyst is easily recycled without noticeable loss of catalytic activity. A detailed kinetic study for C(sp3)–H amination of 1-azido-4-phenylbutane (S1) revealed zero order in the azide substrate and first order in both the catalyst and Boc2O. A cationic iron complex, generated from the neutral precatalyst upon reaction with Boc2O, is proposed as the catalytically active species.