Syntehsis of #alpha#,#alpha#'-Asymmetric Nitroxide Radicals by C-OR O-Acylation of Radical-Enolate Intermediates Generated By Reduction of Homoallylic Nitro Enones with Samarium(II) Iodide

摘要

A new synthetic method to form two structurally different #alpha#, #alpha#'-asymmetric bicyclic nitroxides from the same substrate is described. Reduction of certain homoallylic nitro enones bearing a long alkyl chain witb 3.0 equiv of SmI_2 in THF at -78 deg C gave a nitroxide radical-anion species of type A, while the same reduction followed by addition of HMPA at - 78 deg C resulted in the isomerizationa of the double bond to afford a different nitroxide radical anion species of type C. The former radical-anion undergoes O-acylation by the reaction with acyl chlorides to give #alpha#, #alpha#'-asymmetric bicyclic ester-niroxides of type B, while the later one does C-acylation to produce #alpha#, #alpha#'-asymmetric bicyclic #beta#-diketo nitroides of type D.