Synthesis and characterization of stable 4-(2,2-dicyano-1-t-butyl-ethylene)-2,6-di-t-butylphenoxyl radical

Summary form only given. Stable phenoxyl radicals have been utilized in the study of intermolecular spin interaction phenomena, aimed to synthesize potential organic magnetic materials. One way to enhance the stabilization of phenoxy radicals and the intermolecular spin interactions is to extend the spin conjugation with the introduction of polar functionalities. One of the potential candidate was 4-cyano-2,6-di-t-butylphenoxyl. However, this radical was found to be stable for only 30 min at ambient temperature. Therefore, we modified the structure of 4-cyano-2,6-di-t-butylphenoxyl by replacing the cyano group with t-butyl substituted 2,2-dicyanoethylene group to new functionalized phenoxyl 1. Hindered phenoxyl 1 can be synthesized from malononitrile with the corresponding phenone. To overcome the low reactivity of hindered phenone, a highly reactive ketenimine was utilized to replace the ketone group in phenone. The ketenimine intermediate was generated in-situ in the reaction mixture by reacting alkyl lithium reagent to the corresponding benzonitrile. The synthetic sequence for the preparation of dicyano substituted hindered phenol , based on the ketenimine chemistry, is described. The phenoxyl radical was prepared in benzene with alkaline K/sub 3/Fe(CN)/sub 6/ oxidation. The radical concentration was estimated by the iodometric titration method and found to contain at least 92% of the calculated theoretical molar quantity of radicals.