Palladium-Catalyzed Ligand-Controlled Regioselective Nucleophilic Aromatic Substitution of 1-(Chloromethyl)naphthalenes with Arylacetonitriles.

Abstract

The palladium-catalyzed reaction of 1-(chloromethyl)naphthalenes 1 with (hetero)arylacetonitriles 2 gives either para- or ortho-acylated naphthalenes (3 or 4) in good to high yields. The regioselectivity can be controlled by the ligand of a palladium catalyst. A sterically bulky ligand, tBuPPh2, affords para-acylated products 3, whereas a sterically less bulky ligand, Me2PPh, provides ortho-acylated products 4. Further, direct substitution product 5 at the benzylic position is not obtained essentially, although such a reaction at the benzylic position is favorable in ordinary nucleophilic substitutions. In this paper, it was revealed that the benzylpalladium intermediate could react through a different mode (η3-benzylpalladium intermediate or η1-benzylpalladium intermediate) in nucleophilic aromatic substitution. In addition to the interesting mechanistic aspect, the present reaction provides a facile synthetic method for a wide range of diaryl ketones, some of which are not easily available through the previously known procedures.