Approaches to catalyst discovery. New carbon–heteroatom and carbon–carbon bond formation

Studies on the palladium-catalyzed formation of aryl amines, aryl ethers and a-aryl carbonyl compounds from aryl halides are reported.These studies range from synthetic methodology, to detailed mechanistic analysis, to new methods one can use to screen for catalytic covalent bond formation.Improved methods for formation of aryl ethers and room temperature amination chemistry have resulted from a mechanistic understanding of the reaction.Over the past 20 years, palladium-catalyzed methods for aromatic substitution have provided useful routes to biaryl, alkynyl-aryl and vinyl-aryl compounds [1,2], The palladium-catalyzed formation of aromatic carbon-heteroatom bonds has become a useful synthetic tool in the past few years [3].The new direct formation of a-aryl carbonyl compounds provides a method to form sp 3 -aromatic carbon-carbon bonds [4±7], The purpose of this presentation is to provide examples of C±N, C±O and C±C bond formation that have been developed recently in the author's laboratory and to provide mechanistic information that allows one to understand why one type of catalyst is more effective than another for a particular class of transformation (Scheme 1).