SYNTHESIS OF CHIRAL NITROXIDES AND AN UNUSUAL RACEMIZATION REACTION

Lai's protocol for the synthesis of nitroxides has been extended to th e synthesis of several new chiral piperazine and morpholine nitroxides . This strategy utilizes the Bargellini reaction as the key bond-formi ng step. Several optically pure nitroxides incorporating alpha-aromati c and alpha-spiro centers were prepared by this route. These chiral ni troxides will be of interest as enantioselective oxidants, as traps fo r prochiral radicals, and in the preparation of new materials. One of these nitroxides, compound 43, was found to racemize under mild oxidiz ing conditions. The mechanism for this unusual racemization reaction w as investigated.