Regioselective synthesis of C-prenylated flavonoids via intramolecular [1,3] or [1,5] shift reaction catalyzed by acidic clays

[Display omitted] •Some natural 6-C or 8-C prenylflavonoids 1–7 have been synthesized.•Florisil catalyzes [1,5] shift reaction to provide 8-C prenylflavonoids.•Montmorillonite K10 catalyzes [1,3] shift reaction to obtain 6-C prenylflavonoids.•Florisil and Montmorillonite K10 were effective and eco-friendly catalyst. Prenyl side chain and dihydropyrano skeleton exists in many natural and synthetic biologically active flavonoids. A highly efficient and regioselective method for the synthesis of C-prenylated flavonoids via intramolecular [1,3] or [1,5] shift reaction of 5-O-prenylflavonoids catalyzed by Florisil or Montmorillonite clays is described. Florisil catalyzes intramolecular [1,5] shift reaction of 5-O-prenylflavonoids to obtain 8-C-prenylated flavonoids exclusively, Montmorillonite K10 exhibits the superior selectivity to promote intramolecular [1,3] shift reaction to obtain 6-C-prenylated flavonoids compared with Florisil and Montmorillonite KSF. This method provides a practical process to regioselective synthesize biologically important C-prenylated flavonoids in good yields using commercially available and inexpensive catalyst under mild conditions.