Photoelectrocyclization Reactions of Conjugated Cycloalkenones: Scope and Reactivity

Outlined
here are studies exploring the scope of the sequential
photoelectrocyclization, [1,5]-hydride shift of conjugated bis-aryl
cycloalkenone substrates. We have found not only that the cyclization
precursors can be synthesized in a modular fashion but also that the
cyclization is efficient and amenable to the presence of a range of
cycloalkenones and aromatic systems. Among the interesting discoveries
from this work is that the electrocyclization intermediate can be
competitively captured with protons and that the nature of the excited
state (singlet vs triplet) is dependent on aromatic substitution.