Allylic radicals from methylenecycloalkanes

Abstract

Abstraction of an allylic hydrogen in methylene cyclo-propane, -butane, -pentane, and -hexane affords the corresponding allylic radicals. Their e.s.r. spectra can be detected in appropriate conditions below –100 °C. In the case of the six-membered ring radical the two pseudoaxial and the two pseudoequatorial hydrogens are diastereotopic, thus indicating that, as expected, a half-chair conformation is adopted. On the other hand the five-membered ring radical prefers an envelope conformation, whereas the four-membered ring radical (and obviously the three-membered) are planer.