1431555-56-4Relevant articles and documents
Nonheme iron-mediated amination of C(sp3)-H bonds. Quinquepyridine-supported iron-imide/nitrene intermediates by experimental studies and DFT calculations
Liu, Yungen,Guan, Xiangguo,Wong, Ella Lai-Ming,Liu, Peng,Huang, Jie-Sheng,Che, Chi-Ming
supporting information, p. 7194 - 7204 (2013/06/27)
The 7-coordinate complex [Fe(qpy)(MeCN)2](ClO4) 2 (1, qpy = 2,2′:6′,2″:6″, 2′′′:6′′′,2′′′′- quinquepyridine) is a highly active nonheme iron catalyst for intra- and intermolecular amination of C(sp3)-H bonds. This complex effectively catalyzes the amination of limiting amounts of not only benzylic and allylic C(sp3)-H bonds of hydrocarbons but also the C(sp3)-H bonds of cyclic alkanes and cycloalkane/linear alkane moieties in sulfamate esters, such as those derived from menthane and steroids cholane and androstane, using PhI=NR or "PhI(OAc)2 + H2NR" [R = Ts (p-toluenesulfonyl), Ns (p-nitrobenzenesulfonyl)] as nitrogen source, with the amination products isolated in up to 93% yield. Iron imide/nitrene intermediates [Fe(qpy)(NR)(X)]n+ (CX, X = NR, solvent, or anion) are proposed in these amination reactions on the basis of experimental studies including ESI-MS analysis, crossover experiments, Hammett plots, and correlation with C-H bond dissociation energies and with support by DFT calculations. Species consistent with the formulations of [Fe(qpy)(NTs)2] 2+ (CNTs) and [Fe(qpy)(NTs)]2+ (C) were detected by high-resolution ESI-MS analysis of the reaction mixture of 1 with PhI=NTs (4 equiv). DFT calculations revealed that the reaction barriers for H-atom abstraction of cyclohexane by the ground state of 7-coordinate C NTs and ground state of C are 15.3 and 14.2 kcal/mol, respectively, in line with the observed high activity of 1 in catalyzing the C-H amination of alkanes under mild conditions.
