LOW-TEMPERATURE PREPARATIONS OF UNIMOLECULAR NITROXIDE INITIATORS FORLIVING FREE-RADICAL POLYMERIZATIONS

Low-temperature methods for the preparation of monomeric initiators fo r use in ''living'' free radical olefin polymerizations have been deve loped. Oxidative methods for generating carbon radicals in the presenc e of nitroxide traps such as TEMPO utilize PbO2 with benzylic, alkyl, or phenylhydrazines or CuCl2 with lithium enolates. Photolytic methods employ [Cp(CO)(2)Fe](2) with a benzylic bromide, diphenyl disulfide w ith styrene, or di-tert-butyl peroxide with ethers. The use of di-tert -butyl hyponitrite with ethers generates carbon radicals at 50 degrees C that are trapped by TEMPO.