Palladium-Catalysed Coupling Reactions

Abstract

A review. In this review only these cases were discussed where it seems highly likely that the technol. is or was used for ton-scale prodn. The authors documented twelve cases where the Mizoroki-Heck reaction was used to arylate an alkene. In two of these cases allylic alcs. were arylated, leading to the aldehyde or the ketone. The Suzuki reaction was used mostly to produce biaryl compds. from aryl halides and arylboronic acid derivs. Twelve processes were recorded. O-Tolyl-benzonitrile, a biaryl compd. produced via the Suzuki reaction, was used as an intermediate in six different pharmaceuticals all belonging to the Sartan group of blood pressure-lowering agents. The Kumada-Corriu reaction in which an aryl or alkenyl Grignard is coupled to an aryl or alkenyl halide was used nine times. In these coupling reactions palladium is often replaced by the much cheaper nickel or iron catalysts. The Negishi reaction couples an arylzinc halide with an aryl or alkenyl halide. These reactions are fast and highly selective; the only drawback being the stoichiometric zinc waste. Two cases were found. In one of these it was possible to use only a catalytic amt. of zinc (double metal catalysis). The Sonogashira reaction couples a terminal alkyne to an aryl or alkenyl halide. Three cases were found. Acetylene is usually not coupled as such in view of its instability. Instead, trimethylsilylacetylene or the acetylene acetone adduct was used. Finally, one case was found of a palladium-catalyzed allylic substitution and one case of a CH-activation reaction to form a benzocyclobutane ring. Most of these reactions were implemented in prodn. in the past ten years. [on SciFinder(R)]