Rh(III)-catalyzed (5 + 2)-cycloaddition reactions of ortho-hydroxyethyl phenols with internal alkynes: efficient synthesis of benzoxepines.

An unprecedented (5 + 2)-cycloaddition reaction of ortho-hydroxyethyl phenol and internal alkyne was developed. This Rh(III)-catalyzed reaction provided benzoxepine derivatives which have very high biological significance. A wide range of ortho-hydroxyethyl phenols and internal alkynes were studied to provide the benzoxepines in high yields.