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Paper | Special issue | Vol 54, No. 1, 2001, pp.217-224
Published online, 1st January, 1970
DOI: 10.3987/COM-00-S(I)19
■ Synthesis of α,α'-Asymmetric Nitroxide Radicals by C- or O-Acylation of Radical-enolate Intermediates Generated by Reduction of Homoallylic Nitro Enones with Samarium(II) Iodide

Rui Tamura,* Satoshi Shimono, Kasuke Fujita, and Ken-ichi Hirao

*Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan

Abstract

A new synthetic method to form two structurally different α, α’-asymmetric bicyclic nitroxides from the same substrate is described. Reduction of certain homoallylic nitro enones bearing a long alkyl chain with 3.0 equiv of SmI2 in THF at -78°C gave a nitroxide radical-anion species of type A, while the same reduction followed by addition of HMPA at -78°C resulted in the isomerization 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 α, α’-asymmetric bicyclic ester-nitroxides of type B, while the latter one does C-acylation to produce α, α’-asymmetric bicyclic β-diketonitroxides of type D.