Ozone-mediated nitration of naphthalene and some methyl derivatives with nitrogen dioxide. Remarkable enhancement of the 1-nitro/2-nitro isomer ratio and mechanistic implications

Naphthalene, 1- and 2-methylnaphthalenes were smoothly nitrated with nitrogen dioxide at low temperatures in the presence of ozone to afford the corresponding nitro derivatives in high yields, For naphthalene, the 1-nitro/2-nitro isomer ratios were remarkably high, mostly ranging from 35 to 70, 1,4-Dimethylnaphthalene suffered extensive side-chain substitution under similar conditions, The enhanced regioselectivity as compared with conventional nitrations has been interpreted in terms of the electron transfer mechanism involving the nitrogen trioxide as the initial electrophile.