Reaction of (Arylmethyl)amines with Superoxide Anion Radical in Aprotic Medea. Insights into Cytokinin Senescence Inhibition

Article abstract of DOI:10.1021/jo00158a023

The cytokinins are a group of plant senescence retarding phytohormones, usually N-arylmethyl derivatives of adenine.Purine, adenine, and the cytokinins kinetin <6-(furfurylamino)purine> and 6-(benzylamino)purine were reacted with O2^-. generated from KO2 solubilized in diethylamine by 18-crown-6 polyether.The only reaction observed was simple deprotonation of the N-7 hydrogen, yielding an air-stable salt.In order to uncover other modes that might be available in the absence of this simple acid-base reaction, we reacted various (arylmethyl)amines (i. e., furfurylamine and benzylamine) and (arylmethyl)anilines (2a-c) with O2^-. in benzene.The products in the case of (arylmethyl)amines were the corresponding aroylamines isolated in greater than 60percent yield.Compounds 2a-c yielded the corresponding amides (3), benzoic acids (4), nitrobenzenes (5), and arenes.Similar results were obtained when tert-butoxide or hydroxide replaced superoxide, with the rate of reaction decreasing in the order t-BuO^- > O2^-. > HO^-, the apparent order of decreasing basicity.The results suggest that the process observed involves a base-catalyzed autoxidation of the benzylic carbon of the benzylamines.The resulting hydroperoxide rearranges and/or undergoes oxidative cleavage, ultimately yielding the observed products.Aniline itself reacts with O2^-., yielding azobenzene, nitrobenzene, and (4-nitrophenyl)phenylamine.The latter presumably results from the nitrobenzene trapping of the anilinyl radical.