Stereoselective reduction of indoline nitroxide radicals

Abstract

1,2-Dihydro-2-alkyl-2-phenyl-3H-indol-3-one 1-oxyls (1) and the corresponding amines (6) undergo stereoselective reduction with NaBH₄ giving respectively a pair of diastereoisomeric hydroxylamines (2),(3) and the corresponding amines (7),(8) Both lead to nitroxide radicals (4) and (5), by oxidation; the quantitative ratio of diastereoisomers was determined by means of liquid–liquid chromatography. The configurations of the isomers are tentatively assigned on the basis of ¹H n.m.r. and e.s.r. data, as well as on the stereochemistry of the reaction.