Sequential 1,2-Addition−Electrocyclic Ring Closures Involving Acyclic α,β-Unsaturated Iminiums: A Formal [3 + 3] Cycloaddition Strategy to Unique Pyranyl SpirocyclesRichard P. Hsung, Letitia J. Yao, Christopher D. Morgan et al.|The Journal of Organic Chemistry|1999Cited by 89
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, Luke R. Zehnder et al.|The Journal of Organic Chemistry|2003Cited by 78