ipso- and tele-Substitution pathways in the reactions of 1,3-dimethyl-2,4-dinitro- and 1,3-dimethyl-2-nitro-4-phenylsulphonylnaphthalene with sodium arenethiolates in dimethyl sulphoxide

Abstract

1,3-Dimethyl-2,4-dinitronaphthalene (4) reacts with sodium 2,4,6-trimethylbenzenethiolate in dimethyl sulphoxide at 120 °C giving a mixture of an ipso-substitution product, 1,3-dimethyl-2-nitro-4-(2,4,6-trimethylphenylthio)naphthalene (6a), and of two tele-substitution products, viz. 3-methyl-2-nitro-1-(2,4,6-trimethylphenylthiomethyl)-(7a) and 1-methyl-2-nitro-3-(2,4,6-trimethylphenylthiomethyl)-naphthalene (8a). Lower relative yields of tele-substitution products were obtained when the reaction temperature was decreased and when the less bulky sodium benzenethiolate was used as nucleophile. The reaction of 1,3-dimethyl-2-nitro-4-phenylsulphonylnaphthalene (5) with sodium 2,4,6-trimethylbenzenethiolate (Me₂SO, 120 °C) gave only the tele-substitution products (7a) and (8a). The obtained results show that among the possible ipso- and tele-substitution products only those deriving from the departure of the nucleofugic group present in the α-position are formed. Probable mechanisms accounting for the experimental results are discussed.