Synthesis of Bifunctional Thiophenes via Fiesselmann Condensation of Ynone Trifluoroborate Salts.

Ynone trifluoroborate salts undergo a base-promoted condensation reaction with alkylthiols to generate thiophene boronates with complete regiocontrol. The products are isolated in high yield and can be further derivatized through conventional C-B bond functionalization reactions.