Department of Chemistry & Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, USA.
J Org Chem. 2012 Jul 6;77(13):5600-5. doi: 10.1021/jo300713h. Epub 2012 Jun 13.
A series of cyclometalated palladium complexes derived from O-phenylcarbamates has been synthesized by the reaction of the respective carbamates with Pd(OAc)(2) in the presence of acids, CF(3)CO(2)H, CF(3)SO(3)H, and p-TsOH. The palladacycles were observed to coordinate amines and electron rich anilines but not sulfonamides or carboxamides. Analysis of the (t)Bu-NH(2) adduct of the palladacycle 2b (2b·(t)Bu-NH(2)) by NMR spectroscopy (NOE) revealed a cis-coordination of the amine. However, the amine adducts failed to undergo ortho-amination (C-N bond formation) under varied reaction conditions. Notably, the palladacycle 1d was found to react efficiently with N-iodosuccinimide (NIS) to yield the ortho-iodinated carbamate, 1e. More significantly, this reaction can be extended to a palladium-catalyzed ortho C-H bromination of aryl-O-carbamates even at 5 mol % loading of Pd(OAc)(2) using N-bromosuccinimide (NBS).
一系列源自邻苯二甲酰亚氨基甲酯的环金属钯配合物通过各自的邻苯二甲酰亚氨基甲酯与 Pd(OAc)(2)在酸（CF(3)CO(2)H、CF(3)SO(3)H 和 p-TsOH）存在下反应合成。钯配合物被观察到与胺和富电子苯胺配位，但不与磺胺或羧酰胺配位。通过 NMR 光谱（NOE）对钯配合物 2b 的（t）Bu-NH(2)加合物 2b·(t)Bu-NH(2)进行分析，揭示了胺的顺式配位。然而，在不同的反应条件下，这些胺加合物未能进行邻位胺化（C-N 键形成）。值得注意的是，发现钯配合物 1d 可以与 N-碘代丁二酰亚胺（NIS）有效反应，生成邻碘代氨基甲酸酯 1e。更重要的是，即使在 5 mol % Pd(OAc)(2)负载量下，该反应也可以扩展到芳基-O-邻位 C-H 溴化反应，使用 N-溴代丁二酰亚胺（NBS）。
