The reactivity of organophosphorus compounds. Part XXIX. Deoxygenation of nitroxyl radicals by trialkyl phosphites: a new route to nitrenium ions via electron transfer reactions of aminyl radicals

Abstract

A convenient and mild route to arylnitrenium ions is described: deoxygenation of diphenylnitroxyl by triethyl phosphite in boiling ethanol under nitrogen gives diphenylamine and p-ethoxydiphenylamine. Thermolysis of tetraphenylhydrazine in ethanol gives the same product, thus pointing to the formation of diphenylaminyl radicals which, in part, undergo mutual electron transfer to give diphenylnitrenium ions. In accord with this phenyl-t-butylnitroxyl reacts with triethyl phosphite in methanol to give o- and p-methoxy-N-t-butylanilines in the same ratio as that produced via the authentic nitrenium ion route from N-chloro-N-t-butylaniline in methanol. Diphenylnitroxyl readily dehydrogenates 9,10-dihydroanthracene, the efficiency of the reaction being improved several fold by a cycle involving in situ regeneration of diphenylnitroxyl by aerial oxidation.