ACYLATION OF 2-METHOXYNAPHTHALENE WITH ACYL CHLORIDES IN THE PRESENCE OF A CATALYTIC AMOUNT OF LEWIS-ACIDS

The regiochemistry of the reaction of 2-methoxynaphthalene 1 with benzoyl chloride 2a using a catalytic amount of a Lewis acid is strongly influenced by the identity of the acid catalyst employed as well as by the reaction temperature. By using InCl3, FeCl3, SnCl4 or ZnCl2 and heating at 160 degrees C, 2-benzoyl-6-methoxynaphthalgne 4a is selectively produced along with 1-benzoyl-7-methoxynaphthalene 5a, while in the case of AlCl3, SbCl5 or TiCl4, 1-benzoyl-2-methoxynaphthalene 3a is the major product. 2-Acyl-6-methoxynaphthalenes 4b-e can be selectively obtained using InCl3 and the corresponding acyl chlorides 2b-e in place of 2a. In the presence of a stoichiometric amount of InCl3, the reaction of 1 with 2a also gives 4a as the predominant product along with 5a even at 50 degrees C. This reaction appears to involve isomerisation of 3a to 4a and 5a.