Dibenzothiophene

Dibenzothiophene (DBT, diphenylene sulfide) is the organosulfur compound consisting of two benzene rings fused to a central thiophene ring. It has the chemical formula C12H8S. It is a colourless solid that is chemically somewhat similar to anthracene. This tricyclic heterocycle, and especially its disubstituted derivative 4,6-dimethyldibenzothiophene are problematic impurities in petroleum.

Synthesis and reactions
Dibenzothiophene is prepared by the reaction of biphenyl with sulfur dichloride in the presence of aluminium chloride.

Reduction with lithium results in scission of one C-S bond. With butyllithium, this heterocycle undergoes stepwise lithiation at the 4-position. S-oxidation with peroxides gives the sulfoxide.

Dibenzothiophene is electron-rich, and naturally undergoes aromatic substitution para to the sulfide. Oxidation to the sulfoxide or sulfone leaves the compound electron poor, and substitution occurs at the meta position instead.