EVIDENCE FOR DIAZENYL ALLYL DIRADICALS IN THE THERMOLYSIS OF 4-ALKYLIDENE-1-PYRAZOLINES

Article abstract of DOI:10.1016/0040-4020(82)80164-6

Secondary deuterium kinetic isotope effects indicate that the C-N bond anti to the Me group on 4-ethylidene-1-pyrazoline breaks preferentially to the syn bond.It is suggested that the product determining step involves an intramolecular radical displacement of nitrogen, as well as an electrocyclic rotation of the allylic methylene groups of the diazenyl allyl diradical, to generate the cyclopropane ring concerted with the loss of nitrogen.The position of deuterium in the methylmethylenecyclopropane can best be rationalized by this latter step.