Synthesis of Enantiomerically Pure Nitronyl Nitroxide Radicals Through Chiral Pool

Two pairs of new optically active nitronyl nitroxides derived from N-Boc-D- or L- prolinol are described. The synthetic route consist of (1) the synthesis of chiral aryl aldehydes by Mitsunobu reaction, (2) the condensation of the 2,3- bis(hydroxylamino)-2,3-dimethylbutane with chiral aldehydes to give 1,3-dihydroxyimidazolidine, and (3) the final oxidation of 1,3-dihydroxyimidazolidine with aqueous NaIO4 at 0 °C. These two pairs have been specifically designed for further assessing the differences in activity of chiral nitronyl nitroxides and for developing chiral molecular magnetic material by the metal-radical complexes approach.