Preparation and Properties of New Organic Magentic Material

介绍了一种合成α-不对称双环氮氧化物的新方法。在-50ﾟC下，在四氢呋喃或四氢呋喃-Et_2O中用3当量的SML_2还原某些高烯丙基硝基酮，得到稳定的氮氧化物自由基烯醇基中间体，然后在-50ﾟC下加入亲电试剂如酰氯，导致烯醇基的O-酰化生成相应的中性氮氧化物。还原过程对底物结构、SML_2用量、溶剂组成和反应温度非常敏感。确定了该两步反应的最佳反应条件。当用吸电子基团取代的苯甲酰氯作为O-酰化反应的电泳剂时，以良好到中等的产率分离出分析纯的稳定的氮氧自由基。虽然有机硅氯化物和烷基化试剂作为电泳剂在反应混合物中似乎提供了相应的自由基产物，但没有得到纯的自由基产物。通过电子自旋共振波谱和产物分析，探讨了氮氧自由基烯醇酸中间体的形成机理。

A new methodology for the synthesis of alpha-asymmetric bicyclic nitroxides is described. Reduction of certain homoallylic nitroenone with 3.0 equiv of Sml_2 in THF or THF-Et_2O at-50ﾟC gave a stable nitroxide radical-enolate intermediate, a kind of radical-anion species.The subsequent addition of electrophiles such as acyl chlorides at-50ﾟC resulted in the O-acylation of the enolate moiety to form the corresponding neutral nitroxide radical. The reduction process was quite sensitive to the substrate structure, amount of Sml_2, solvent composition and reaction temperature. The optimum reaction conditions for this two-step reaction were determined. Analytically pure stable nitroxide radicals were isolated in good to fair yields when benzoyl chlorides substituted by electron-withdrawing groups were used as the electrophile for O-acylation. Although the use of organosilyl chlorides and alkylating reagents as the electrophile seemd to provide the corresponding radical products in the reaction mixture, pure redical products were not obtained. The mechanism of formation of the nitroxide radical-enolate intermediate was investigated by ESR spectroscopy and the product analysis.