Origin of the Regiochemistry in the Photochemical Cycloaddition Reaction of 2-Cyclopentenone with Allene: Trapping of Triplet 1,4-Biradical Intermediates with Hydrogen Selenide

Article abstract of DOI:10.1016/S0040-4039(00)60429-X

The photochemical cycloaddition reaction between 2-cyclopentenone and allene in toluene at -78 deg C yields cyclobutane adducts with head-to-head and head-to-tail regiochemistry in a ratio of 88:12.In the presence of high concentrations of hydrogen seleni