The homogeneous catalytic hydrosilation-hydrogenation of pyridines is observed in the presence of Cp2TiMe2 (Cp = η5-C5H5) and CpCp*TiMe2 (Cp* = η5-C5Me5) as catalysts and using PhSiH3 or PhMeSiH2 as the source of Si-H. Under appropriate conditions, and with appropriate ring-substitution, good yields of the N-silyl-dihydropyridine or N-silyltetrahydropyridine products are be obtained. Although complete saturation is not achieved with organosilane alone, carrying out the reaction under moderate H2 pressures can give excellent yields of N-silylpiperidines. Under moderate pressures of H2, [Cp2TiH]2 catalyzes rapid H-D exchange between H2 and the 2- and 6-positions of C5D5N. Under the same conditions, only traces of hydrogenation are observed. This, together with the regioselectivity of 3-picoline hydrosilation-hydrogenation, leads to the conclusion that the key step in the reaction is probably addition of Ti-Si to C=N.Key words: hydrosilation, hydrogenation, pyridines, dimethyltitanocene, catalysis.
在使用Cp2TiMe2(Cp = η5-
C5H5)和CpCp*TiMe2(Cp* = η5-C5Me5)作为催化剂,以及PhSiH3或PhMeSiH2作为Si-H来源的条件下,观察到了均相催化的
吡啶加氢
硅化反应。在适当的条件下,以及适当的环取代,可以获得较好的N-
硅基-
二氢吡啶或N-
硅基-四氢
吡啶产物的收率。尽管单独使用有机
硅烷无法实现完全饱和,但在中等H2压力下进行反应可以得到极好的N-
硅基-
哌啶收率。在中等H2压力下,[Cp2TiH]2催化了H2与C5D5N的2-和6-位置的快速H-D交换。在相同条件下,仅观察到微量的加氢反应。这,加上3-
皮考啉加氢
硅化-加氢反应的区域选择性,导致我们得出结论,反应的关键步骤可能是Ti-Si与C=N的加成。关键词:加氢
硅化,加氢,
吡啶,二甲基
钛环戊烯,催化。