Intra- and Intermolecular Hydroamination of Alkynes Catalyzed by ortho-Metalated Iridium Complexes
Resource
Organometallics 26 (4): 1062-1068
Journal
Organometallics
Journal Volume
26
Journal Issue
4
Pages
1062-1068
Date Issued
2007
Date
2007
Author(s)
Abstract
Reaction of o-(diphenylphosphino)(N-benzylidene)aniline (P∼;N) with [Ir(COD)Cl]2 affords the substitution product [(P∼N)Ir(COD)Cl] (1). Treatment of 1 with AgBF4 yields the cyclometalated indium hydride complex [P,MC-(P∼N)Ir(COD)H]BF4 (2). On the other hand, under atmospheric pressure of CO, carrying out the substitution of [Ir(COD)Cl]2 with P∼N results in the formation of [P,N,C-(P∼N)-Ir(CO)HCl] (5). Conversion of 4 into 5 can be achieved by the reaction of 4 with CO in the presence of tetraethylammonium chloride. Both 4 and 5 are characterized by spectroscopic and X-ray structural analyses. All iridium complexes are not good catalysts for hydroamination. However, the combination of 5 with NaB[3,5-C6 H3(CF3)2] 4 (denoted as NaBAr4F) provides a potent catalytic system for both intraand intermolecular hydroamination of alkynes. Intramolecular reaction of o-(2-phenylethynyl)anilines produces the corresponding indoles in good yields. Furthermore, intermolecular hydroamination takes place smoothly to generate the imine intermediates, which could be subsequently reduced by triethylsilane using the same catalyst, giving N-silylated amines. However, the N-silylated amines readily hydrolyze to produce secondary amines. © 2007 American Chemical Society.
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