Chapter One

1.1 Characteristic Features of Pd-Promoted or -Catalyzed Reactions

There are several features which make reactions involving Pd catalysts and reagents particularly useful and versatile among many transition metals used for organic synthesis. Most importantly, Pd catalysts offer an abundance of possibilities of carbon-carbon bond formation. Importance of the carbon-carbon bond formation in organic synthesis needs no explanation. No other transition metals can offer such versatile methods of the carbon-carbon bond formations as Pd. Tolerance of Pd catalysts and reagents to many functional groups such as carbonyl and hydroxy groups is the second important feature. Pd-catalyzed reactions can be carried out without protection of these functional groups. Although reactions involving Pd should be carried out carefully, Pd reagents and catalysts are not very sensitive to oxygen and moisture, and even to acid in many reactions catalyzed by Pd-phosphine complexes. It is enough to apply precautions to avoid oxidation of coordinated phosphines, and this can be done easily. On the other hand, the Ni(0) complex is extremely sensitive to oxygen.

Of course, Pd is a noble metal and expensive. Its price frequently fluctuates drastically. A few years ago, Pd was more expensive than Pt and Au but cheaper than Rh. As of October 2003, the comparative prices of the noble metals were: Pd 1), Au (1.8), Rh (2.8), Pt (3.3), Ru (0.2). Recently the price of Pd has dropped dramatically, and Pt is currently t