Mechanistic insights into the PdII-catalyzed chemoselective N-demethylation vs. cyclometalation reactivity pathways in 1-Aryl-N,N-dimethylethanamines

• Main Authors: Yap, Jeanette See Leng, Ding, Yi, Yang, Xiang-Yuan, Wong, Jonathan, Li, Yongxin, Pullarkat, Sumod A., Leung, Pak-Hing
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2014
• Subjects: DRNTU::Science::Chemistry::Inorganic chemistry
• Online Access: https://hdl.handle.net/10356/105314; http://hdl.handle.net/10220/20485; http://dx.doi.org/10.1002/ejic.201402547
• Institution: Nanyang Technological University

Two structurally isomeric substituted N,N-dimethylethanamines have been prepared. Treatment of the 2,4-di-tert-butylphenyl isomer with PdII ions generated the ortho-metalated complexes. On the other hand, treatment of the 2,5-di-tert-butylphenyl-substituted amine resulted in the unexpected chemoselective cleavage of one of the three N–C bonds, thus generating the corresponding secondary amine. The N-demethylation process could be catalyzed at room temperature by palladium(II) catalysts such as PdCl2 or Pd(OAc)2. Furthermore, treatment with a stoichiometric amount of PdII ions gave a metal complex in which both secondary amines were bound to Pd in an N-monodentate fashion. When triethylamine was introduced, one of the N-ethyl groups in NEt3 was cleaved, and an unexpected heteroamine complex was produced. The products generated were isolated and characterized by X-ray crystallography. Mechanistic insights into the cyclometalation and C–N cleavage observed are discussed.