Mechanistic Studies of Wacker-Type Intramolecular Aerobic Oxidative Amination of Alkenes Catalyzed by Pd(OAc)(2)/Pyridine

作者：Ye Xuan; Liu Guosheng; Popp Brian V; Stahl Shannon S^*

来源：Journal of Organic Chemistry, 2011, 76(4): 1031-1044.

DOI：10.1021/jo102338a

Wacker-type oxidative cyclization reactions have been the subject of extensive research for several decades, but few systematic mechanistic studies of these reactions have been reported. The present study features experimental and DFT computational studies of Pd(OAc)(2)/pyridine-catalyzed intramolecular aerobic oxidative amination of alkenes. The data support a stepwise catalytic mechanism that consists of (1) steady-state formation of a Pd-II-amidate-alkene chelate with release of 1 equiv of pyridine and AcOH from the catalyst center, (2) alkene insertion into a Pd-N bond, (3) reversible beta-hydride elimination, (4) irreversible reductive elimination of AcOH, and (5) aerobic oxidation of palladium(0) to regenerate the active trans-Pd(OAc)(2)(py)(2) catalyst. Evidence is obtained for two energetically viable pathways for the key C-N bond-forming step, featuring a pyridine-ligated and a pyridine-dissociated Pd-II species. Analysis of natural charges and bond lengths of the alkene-insertion transition state suggest that this reaction is best described as an intramolecular nucleophilic attack of the amidate ligand on the coordinated alkene.

• 出版日期2011-2-18