Tin(IV) Chloride-Chiral Pyrogallol Derivatives as New Lewis Acid-Assisted Chiral Brønsted Acids for Enantioselective Polyene Cyclization

New Lewis acid-assisted Bronsted acids (LBAs), tin(IV) chloride-2,6-dialkoxyphenols, serve as artificial cyclases for biomimetic polyene cyclization. For example, the enantioselective cyclization of 4-(homogeranyl)toluene using tin(IV) chloride-2,6-di[(1‘R,2‘R)-trans-2‘-(3‘ ‘,5‘ ‘-xylyl)cyclohexanoxy]phenol gave a trans-fused tricyclic compound with 85% ee.