Department of Chemistry, The University of Vermont, 82 University Place, Burlington, Vermont 05405, USA.
J Am Chem Soc. 2012 Jun 20;134(24):9890-3. doi: 10.1021/ja303054c. Epub 2012 Jun 8.
We report that 1-aza-2-azoniaallene salts, generated from α-chloroazo compounds by treatment with halophilic Lewis acids, participate in intramolecular C-H amination reactions to provide pyrazoline products in good to excellent yield. This intramolecular amination occurs readily at both benzylic and tertiary aliphatic positions and proceeds at an enantioenriched chiral center without loss of enantiomeric excess. A competition reaction shows that insertion occurs more readily at an electron-rich benzylic position than an electron-deficient one. These observations are consistent with the 1-aza-2-azoniaallene intermediate reacting as a nitrenium-like ion by a concerted insertion mechanism.
我们报告说，由α-氯代偶氮化合物与嗜盐路易斯酸处理生成的 1-氮杂-2-氮杂烯盐参与分子内 C-H 氨化反应，以良好至优异的产率提供吡唑啉产物。这种分子内氨化反应在苄位和叔脂肪族位置都很容易发生，并在手性中心进行对映体富集，而不会失去对映体过量。竞争反应表明，插入反应更容易发生在富电子的苄位，而不是缺电子的苄位。这些观察结果与 1-氮杂-2-氮杂烯中间体通过协同插入机制反应作为类似氮烯的离子一致。
