Competition betweenS-oxidation and nitration in reactions of some β- and γ-quinolinyl sulfides with nitrating mixture

This study was performed in order to explain different orientation in the reaction of quinolinyl sulfides with nitrating mixture, which converted on one hand quinolinyl sulfides 1, 3 and 5 to sulfoxides 2, 4 and 8, respectively, on the other hand, sulfides 6, 7 to the respective nitroderivatives 9 and 10. Competitive experiments showed following reactivity order: thianthrene 11 ≥ thianthrene 5-oxide 12 ≥ isothioquinanthrene 3 ≥ thioquinanthrene 1 ≥ 3,3′-diquinolinyl sulfide 5 ≥ 3,4′-diquinolinyl sulfide 6 ≥ 4,4′-diquinolinyl sulfide 7. Considering that NO2+ (as reactive form of nitrating mixture) attacks the most electronodonating (sulfur or carbon) center the reactivity order well correlates with the results of HOMO as well as MEP calculations.