Reprinted from the Journal of the Chemical Society, Chemical Communications, 1993, 1836-1838 (1993).
©Royal Society of Chemistry, 1993.
William J. Leigh* and J. Alberto Postigo
Contribution from the Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1
Abstract: The photochemistry of the E,E- and E,Z-geometric isomers of 1,2-bis(ethylidene)cyclopentane and -cyclobutane, and 2,3-bis(ethylidene)norbornene has been studied in hydrocarbon solution at room temperature; the results are inconsistent with the classical theoretical models for diene cis,trans-photoisomerization and ring closure, which assume that both processes involve only simple torsional motions about (one or both of) the termini of buta-1,3-diene.