Pentamethylated and pentaphenylated azaferro- and azaruthenocenes: simple and general methodology for the preparation of enantiopure derivatives.
Pentamethylated and pentaphenylated azaferro- and azaruthenocenes: simple and general methodology for the preparation of enantiopure derivatives.
复制标题
五甲基化和五苯基化氮杂铁和氮杂并茂：制备对映体纯衍生物的简单而通用的方法。
DOI：
10.1021/jo026333r
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
M. Johannsen
中科院分区：
文献类型：
--
作者：
J. G. Hansen;M. Johannsen
报道了一种对映选择性合成平面手性 2-取代 1',2',3',4',5'-五甲基氮杂二茂铁和氮杂并茂化合物的方法。关键步骤是通过选择性邻位锂化引入对映体纯手性亚砜助剂，随后对所得非对映体进行色谱分离。通过用叔丁基锂处理裂解掉亚砜辅助物，产生光学纯的阴离子，该阴离子可以用各种亲电子试剂猝灭，得到光学纯的氮杂茂金属衍生物。此外，还尝试扩展该方法以涵盖1',2',3',4',5'-五苯基衍生物。然而，不可能将手性亚砜辅助剂连接到五苯基化氮杂二茂铁上，并且对于氮杂茂的情况，只能分离出一种非对映异构体。最重要的是，亚砜基团可以被裂解，所得的手性氮杂茂基阴离子可以用多聚甲醛和碘猝灭，从而得到 ee 值分别为 85% 和 99% 的产物。
A methodology for the enantioselective synthesis of planar chiral 2-substituted 1',2',3',4',5'-pentamethylazaferro- and azaruthenocenes is reported. The key step is the introduction of an enantiopure chiral sulfoxide auxiliary via a selective ortho-lithiation with subsequent chromatographic separation of the resulting diastereomers. Cleaving off the sulfoxide auxiliary by treatment with t-BuLi generates an optically pure anion which may be quenched with a variety of electrophiles to give the optically pure azametallocene derivatives. In addition, it was attempted to extend the methodology to encompass 1',2',3',4',5'-pentaphenyl derivatives. It was, however, not possible to attach the chiral sulfoxide auxiliary onto the pentaphenylated azaferrocene, and for the azaruthenocene case, only one diastereomer could be isolated. Most importantly, the sulfoxide group could be cleaved off and the resulting chiral azaruthenocenyl anion was quenched with paraformaldehyde and iodine, resulting in products with ee values of 85% and 99%, respectively.