Intramolecular electrocyclic reactions. Part I. Structure of ‘bromohydroxyphorone’: 3-bromo-5-hydroxy-4,4,5,5-tetramethylcyclopent-2-enone

Abstract

αα′-Dibromophorone (3,5-dibromo-2,6-dimethylhepta-2,5-dien-4-one) as the conjugate acid undergoes intramolecular electrocyclic addition to give 3-bromo-5-hydroxy-4,4,5,5-tetramethylcyclopent-2-enone. The reactions of this substance, its bromine-free analogue and their derivatives, recorded by Ingold and Shoppee in 1928, are clarified and reinterpreted.