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

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