A practical approach to the synthesis of insect antifeedant tonghaosu analogs

Tonghaosu and its analogs are a class of structurally interesting spiroketal enol‐ether compounds. A practical route to furandiol, a key intermediate for their syntheses, was developed. Using Friedel‐Crafts benzoylation of 3‐(2‐fury I) propyl acetate, a diarylketone was obtained in high yield, which was further transformed into corresponding furandiol by reduction with NaBH₄ in basic medium with simultaneous ester hydrolysis. The furandiol was then cyclized into the desired spiroketal enol‐ether compound in the presence of CuSO₄ 5H₂O.