Novel Alkylidenating Agents via the α Lithiation of Monoalkyl Group 4 Metal Derivatives: Methylidene-Metal Complexes and Their Active Lithiated Precursors
作者:John J. Eisch、Adetenu A. Adeosun
DOI:10.1002/ejoc.200400808
日期:2005.3
The interaction of the Group 4 metal chlorides, MCl4, where M = Ti, Zr, Hf, with two equiv. of methyllithium at –78 °C in toluene has led to the corresponding methylidene-metal complex, H2C=MCl2, possibly complexed with LiCl. That this complex was stable to at least –40 °C was demonstrated by adding chemical trapping agents at this temperature: 1) benzophenone was quantitatively converted into 1,1-diphenylethylene
第 4 族金属氯化物 MCl4(其中 M = Ti、Zr、Hf)与两个当量的相互作用。在–78 °C 时,甲基锂在甲苯中生成相应的亚甲基金属络合物,H2C=MCl2,可能与 LiCl 络合。通过在该温度下添加化学捕集剂证明该复合物在至少 –40 °C 下是稳定的:1) 当 M = Ti 或 Zr 时,二苯甲酮定量转化为 1,1-二苯基乙烯;使用 Hf 类似物,产生了 1,1-二苯基乙烯和 1,1-二苯基乙醇的 1:3 混合物;2) 苯丙酮与亚甲基络合物反应生成 2-苯基-1-丁烯,38% (M = Ti) 或 25% (M = Zr),其中大部分苯丙酮被回收(未反应的酮归因于烯醇化物)与甲基化竞争的盐形成);3)二苯乙炔与H2C=TiCl2通过环加成反应,产率为50%,最终得到α-甲基-顺式-二苯乙烯和α-甲基-反式-二苯乙烯的1:1混合物;最后4) 降冰片烯在ROMP 过程中由亚甲基-钛