THE NITRATION OF ALPHA-ACYLNAPHTHALENES AND BETA-ACYLNAPHTHALENES

The nitration of alpha- and beta-acylnaphthalenes with copper(II) nitr ate in acetic anhydride or nitric acid/acetic acid mixtures gives high yields of the corresponding mononitro compounds. The assignment of co nstitution to these products is made on the basis of extensive H-1 n.m .r. chemicl shift and coupling constant data. In the case of alpha-acy lnaphthalenes, with the notable exception of alpha-pivalonaphthone, ni tration occurs in the alpha-positions of the unsubstituted ring to giv e mixtures of 5- and 8-nitro compounds. alpha-Pivalonaphthone gives ap preciable amounts of the 4-nitro compound and also of the 8-nitro comp ound. This result indicates that the pivaloyl group does not shield th e 8-position sterically to any significant extent and is effectively e lectronically neutral, unlike the other acyl substituents, in allowing attack at the alpha-position (position 4) of the acylated ring. This result is ascribable to the lack of coplanarity of the pivaloyl group with the naphthalene system. All of the beta-acylnaphthalenes gave mix tures of 4-, 5- and 8-nitro derivatives in proportions that did not va ry significantly with the nature of the acyl group.