Synthesis of benzothiophene analogues of ketoconazole and itraconazole

The synthesis of the benzothiophene analogues of the orally active antifungal agents ketoconazole and itraconazole 3a and 3b is reported. The key heterocyclic system 3‐(1‐piperazinyl)benzo[b]thiophene is prepared by formation of the enamine between a benzothienone and ethyl 1‐piperazinecarboxylate. After elaboration of the respective N‐substituents, the methoxy group is cleaved with boron tribromide, and O‐alky‐1ated with the corresponding mesylates.