A Formal [3 + 3] Cycloaddition Reaction. Improved Reactivity Using α,β-Unsaturated Iminium Salts and Evidence for Reversibility of 6π-Electron Electrocyclic Ring Closure of 1-OxatrienesHong C. Shen, Craig A. Zificsak, Heather M. Sklenicka et al.|The Journal of Organic Chemistry|2003Cited by 78