Lee Melissa, Sanford Melanie S
Department of Chemistry, University of Michigan , 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
J Am Chem Soc. 2015 Oct 14;137(40):12796-9. doi: 10.1021/jacs.5b09099. Epub 2015 Oct 6.
This Communication describes the terminal-selective, Pt-catalyzed C(sp(3))-H oxidation of aliphatic amines without the requirement for directing groups. CuCl2 is employed as a stoichiometric oxidant, and the reactions proceed in high yield at Pt loadings as low as 1 mol%. These transformations are conducted in the presence of sulfuric acid, which reacts with the amine substrates in situ to form ammonium salts. We propose that protonation of the amine serves at least three important roles: (i) it renders the substrates soluble in the aqueous reaction medium; (ii) it limits binding of the amine nitrogen to Pt or Cu; and (iii) it electronically deactivates the C-H bonds proximal to the nitrogen center. We demonstrate that this strategy is effective for the terminal-selective C(sp(3))-H oxidation of a variety of primary, secondary, and tertiary amines.
本通讯报道了在无需导向基团的情况下，通过铂催化实现脂肪族胺的端基选择性C(sp(3))-H氧化反应。以化学计量的氯化铜作为氧化剂，在低至1 mol%的铂负载量下反应仍能高产率进行。这些转化反应在硫酸存在下进行，硫酸与胺底物原位反应形成铵盐。我们认为胺的质子化至少起到三个重要作用：（i）使底物可溶于水相反应介质；（ii）限制胺氮与铂或铜的结合；（iii）使氮中心附近的C-H键在电子上失活。我们证明该策略对于多种伯胺、仲胺和叔胺的端基选择性C(sp(3))-H氧化是有效的。
