Regioselective C-H Arylation of 3-Methoxythiophene

Significance

The authors reported a highly regio­selective C-H arylation of 3-methoxythiophene with selected aryl bromides or iodides in a polar medium, catalyzed by Pd(OAc)₂ or PdCl₂. The proposed mechanism involves an electrophilic substitution of the ArPd⁺ X^- species on the electron-rich 2-position of 3-methoxythiophene, followed by a reductive elimination. This arylation reaction was also successfully applied to 3,4-ethylenedioxythiophene (EDOT), to produce EDOT containing conjugated oligomers. Additionally, the authors proposed that this methodology could be extended to synthesis of conjugated polymers, such as poly(3,4-ethylenedioxythiophene) (PEDOT).