Chupakhin Oleg N, Utepova Irina A, Varaksin Mikhail V, Tretyakov Evgeny V, Romanenko Galina V, Stass Dmitry V, Ovcharenko Victor I
Urals State Technical University, Mira street, 19, 620002 Ekaterinburg, Russian Federation.
J Org Chem. 2009 Apr 3;74(7):2870-2. doi: 10.1021/jo900085s.
We show that the S(N)(H) approach opens up new possibilities in the synthesis of hetaryl-substituted nitronyl nitroxides. The reaction of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl lithium salt with pyridine-, pyrimidine-, pyrazine-, isoquinoline-, phthalazine-, quinoxaline-, and 1,2,4-triazine-N-oxides readily gives rise to the corresponding paramagnetic hetarenes. The reaction of this salt with quinoxaline-1,4-dioxide enabled the synthesis of the first nitronyl nitroxide biradical with two spin-labeled fragments in the vicinal positions of the heteroaromatic cycle; the persistent biradicals of this type were not known earlier. The characterizations of all persistent radicals obtained by S(N)(H) synthetic strategy include X-ray crystal structures, EPR investigation, and static magnetic susceptibility measurements.
我们表明，S(N)(H)方法为合成杂芳基取代的硝酰基氮氧化物开辟了新的可能性。4,4,5,5-四甲基-4,5-二氢-1H-咪唑-3-氧化物-1-氧基锂盐与吡啶、嘧啶、吡嗪、异喹啉、酞嗪、喹喔啉和1,2,4-三嗪-N-氧化物的反应很容易生成相应的顺磁性杂芳烃。该盐与喹喔啉-1,4-二氧化物的反应使得能够合成第一个在杂芳环邻位带有两个自旋标记片段的硝酰基氮氧化物双自由基；这种类型的持久性双自由基以前并不为人所知。通过S(N)(H)合成策略获得的所有持久性自由基的表征包括X射线晶体结构、电子顺磁共振研究和静态磁化率测量。
