The study of late transition elements has gained increasing momentum in recent years because of their potential for catalyzing desirable transformations. A key feature of these metals is that they tend to be both more tolerant to functional groups and more robust toward air and moisture than other transition metals. In part because of these desirable properties, industrially important late metal polymerization catalysts are now under intense scrutiny. Furthermore, late transition metal systems are being studied for their ability to couple the activation and oxidation of light hydrocarbon substrates.
To build new molecular systems relevant to these and related goals, complexes supported by robust, anionic chelating ligands are being pursued. One type of anionic chelating ligand that has shown promise in the development of complexes with transition metal elements is the tridentate “pincer” type ligand. Rhodium (I) 1,3-bis[(di-tert-butylphosphino)methyl]-2,4,6-methylbenzine) (PCP) pincer complexes have been studied for use in selective C—C versus C—H bond activation (Sundermann et al. J. Am Chem. Soc. 122:7095-7104 (2000)). In addition, the use of iridium PCP pincer complexes in the regioselective formation of a-olefins has also been studied (Liu et al. J. Am. Chem. Soc. 121:4086-4087 (1999)).
The tridentate ligand bis(8-quinilinyl)amine (BQAH) and its derivatives are a family of ligands that afford rich reaction chemistry in the formation of transition metal complexes.
Methods for producing BQAH: utilize a modified Bucherer reaction and take not only seven days for completion (Jensen et al. Acta Chem. Scand. 18:1-10 (1964)), but typically provide low yields of 4-8%. Therefore, there is a need for a faster and more efficient method for synthesizing these ligands.
The instant invention addresses that need by using a Pd0 catalyst in conjunction with a catalyst activator to quickly and efficiently synthesize BQAH and derivatives thereof with yields of greater than 80%.