TRAPPING OF THE CYANO RADICAL - DOES IT EVER HAPPEN

The possible trapping of the cyano radical by alpha-phenyl-N-tert-buty lnitrone (PBN) has been probed by a new method Tor the generation of C N., photolysis of N-cyanosuccinimide with PBN. Only in 1,1,1,3,3,3-hex afluoroprppan-2-ol was EPR spectral evidence obtained for the formatio n of a true spin adduct, namely the isocyano adduct of PBN. In other s olvents, like dichloromethane or acetonitrile. the photolysis reaction took an entirely different course and gave the N-cyano-3-succinimidyl adduct of PBN and a second aminoxyl of unknown structure. The same pa ir of adducts could be obtained by photolysis of N-cyanomaleimide and PBN in a reductive coupling reaction. Maleimide gave a similar but cle arly different pair of spectra. The possibility that the cyano or isoc yano PBN adduct might undergo spontaneous hydrolysis to give the amino formyl or formylamino adduct, respectively, was explored. It was shown that the authentic cyano adduct does not give the aminoformyl adduct under hydrolytic conditions. Since there is no method to prepare the i socyano adduct for such experiments, the problem of its hydrolytic rea ctivity is still open. The aminoformyl adduct of PBN was prepared by a ddition of the formamide anion to PBN, followed by oxidation by nickel peroxide, and characterized by its EPR spectrum.