Relationships between Structures and Reactivities in the Oxidation of Benzothiophene and Dibenzothiophene Derivatives

The relationships between structure and reactivity of thiophene derivatives were studied with different degrees of aromatic condensation and numbers of methyl groups. Reactivity of benzothiophene was lower compared to dibenzothiophene (DBT), whereas reactivity of benzonaphthothiophene was like that of DBT. Reactivity of 2-methybenzothiophene was higher than that of benzothiophene. Methyl group at the 2-position of benzothiophene caused no steric hindrance to approach of the oxidants. Methyl groups at the 4- and/or 6-positions of DBT showed different effects depending on the reaction conditions and the nature of the active species.