Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
J Am Chem Soc. 2009 Nov 4;131(43):15615-7. doi: 10.1021/ja904589k.
Studies are described that were designed to determine the structure of the active catalyst in the asymmetric catalytic aziridination of imines with ethyl diazoacetate (AZ reaction). Evidence suggests that the active catalyst contains a boroxine ring in which one of the three boron atoms is spiro-fused with the two phenol groups of the VAPOL ligand. (11)B and (1)H NMR evidence supports the boroxinate structure B in which the counterion to the boroxinate is the protonated form of the imine. The boroxinate structure is also supported by two solid state structures of a VAPOL boroxinate in which the gegen cation is tetramethyl ammonium and 4-dimethylaminopyridinium.
研究旨在确定在不对称催化亚胺与重氮乙酸乙酯的氮丙啶化反应(AZ 反应)中活性催化剂的结构。有证据表明,活性催化剂含有一个硼酸酯环,其中三个硼原子之一与 VAPOL 配体的两个苯酚基团螺环融合。(11)B 和(1)H NMR 证据支持硼酸酯结构 B,其中硼酸酯的反离子是亚胺的质子化形式。硼酸酯结构还得到了 VAPOL 硼酸酯的两个固态结构的支持,其中反离子分别为四甲基铵和 4-二甲基氨基吡啶鎓。