Conformationally-rigid methyl-substituted cyclopropyl ketones with a suitably disposed γ- hydrogen undergo thermal type II reactions efficiently. Comparison of yields of these rearrangements with their photochemical analogs suggest that photochemical type II reactions arise from excited vibrational states. In the absence of a suitably disposed γ- hydrogen, and if strain factors permit, such systems undergo oxovinylcyclopropane to ...
