An electron spin resonance investigation of the products of the Friedel–Crafts reaction of sulphur dioxide with methylnaphthalenes

Abstract

A series of mono-, di-, tri-, tetra-, and hexa-methylnaphthalenes, and naphthalene were reacted with AlCl₃–SO₂, AlCl₃–SOCl₂, or AlCl₃–S₂Cl₂, using CH₂Cl₂ as solvent. The radical cation products produced were studied using e.s.r. 1,4-, 1,5-, and 1,8-dimethyl-, 1,2,4-trimethyl-, 1,2,3,4- and 1,3,5,7-tetramethyl-, 1,2,3,4,5,8-hexamethyl-, and octamethyl-naphthalene all gave predominantly spectra from the monomer cation radical. Naphthalene, 1- and 2-methyl- and 1,3-, 1,6-, 1,7-, 2,3-, 2,6-, and 2,7-dimethylnaphthalene gave predominantly spectra ascribed to methyl derivatives of naphtho[1,8-cd]-1,2-dithiole. Spectra from these compounds also contained a significant component which was ascribed to methylperylenes formed from the Scholl condensation of the parent compound. A species described as 3H, 10H-acenaphtho[1,2-c]-1,2-dithiete was observed as a minor product in the reactions with 1,8-dimethylnaphthalene.