Intramolecular Etherification and Polyene Cyclization of π‑Activated Alcohols Promoted by Hot Water

Hot
water, acting as a mildly acidic catalyst, efficiently promoted
intramolecular direct nucleophilic substitution reactions of unsaturated
alcohols with heteroatom or carbon nucleophiles. In a mixed solvent
of water and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), polyene cyclizations
using allylic alcohols as initiators gave the desired cyclized products,
and in neat HFIP, a tricyclization reaction gave a tetracyclic product
in 51% chemical yield.

作为弱酸性催化剂的热水可高效催化不饱和醇与杂原子或碳亲核试剂的分子内直接亲核取代反应。在水与1,1,1,3,3,3-六氟-2-丙醇（HFIP）组成的混合溶剂中，以烯丙醇为引发剂的多烯环化反应可得到目标环化产物；而在纯HFIP溶剂中，三环化反应以51%的化学收率获得了四环产物。