The formation of aryl-carbon and aryl-heteroatom bonds using copper(I) catalysts
Abstract (Summary)Copper(I) complexes of type [Cu(PPh3 )3 X] (where X: Br, Cl), [Cu(PPh3 )2 NO3 ], Cu(L)(PPh 3 )2 X (where X: PF6 , NO3 , ClO4 and L: phenanthroline, diimine, neocuproine), Cu(L)(PPh3 )X (where X: Br and L: phenanthroline, di-imine, neocuproine) are synthesized and characterized to study their catalytic activities in carbon-heteroatom bond formation reactions. The geometrical parameters illustrate that there is a correlation between bite angles and copper-phosphorous bond lengths in mononuclear chelated copper(I) complexes. These complexes had wider bite angles than mononuclear non-chelated copper(I) complexes. Screening of the mononuclear copper(I) complexes in aryl-oxygen bond formation reactions show that the complexes [Cu(PPh3 )3 Br] and [Cu(neocup)(PPh3 )Br] catalyzed the formation of a range of substituted diphenyl ethers at 20 mol% and 10 mol% catalyst loadings respectively. The polynuclear copper(I) complexes fail to catalyze the same reaction. In aryl-nitrogen bond formation reactions, the same complexes [Cu(PPh3 )3 Br] and [Cu(neocup)(PPh 3 )Br] enable the formation of a range of diaryl and triaryl amines. The protocol with [Cu(PPh3 )3 Br] is used for the successful synthesis of o.o' .o '' -amino-trisbenzoic acid-trimethylester at 170Ã?Â°C in o -dichlorobenzene. This molecule is eluded by the Hartwig-Buchwald protocol. The well-defined complex [Cu(neocup)(PPh3 )Br] is further investigated for the formation of aryl-sulfur and aryl-selenium bonds. Optimization and control experiments in this area show that using neocuproine as an additive with CuI, in the presence of NaOt -Bu, in toluene allows the development of protocols for a range of aryl-sulfides and aryl-selenides. In the second protocol, the change of base to K2 CO3 allows the coupling of a range of electron-poor iodides to the respective diaryl selenides. The observed results point to the potential of copper(I) catalysts as alternatives to palladium-based protocols, for the formation of aryl-O, N, S and Se bonds under mild conditions.
School Location:USA - Massachusetts
Source Type:Master's Thesis
Date of Publication:01/01/2003