Improved Turnover Numbers in Palladium-Catalyzed Bisdiene Cyclization-Trapping using N-Heterocyclic Carbene Ligands
作者:James M. Takacs、Suman Layek、Hector Palencia、Ross N. Andrews
DOI:10.1002/adsc.200505136
日期:2005.12
An optimized palladium-N-heterocyclic carbene catalyst system effects the palladium-catalyzedbisdienecyclization-trapping with phenol at the 0.01% catalyst loading level with a TON of 7.6×103 and TOF of 280 h−1, values much higher than typically found for this and related carbocyclizations. The reaction scales well and the trans-substituted six-membered ring product is obtained in excellent yield
优化的钯-N-杂环卡宾催化剂体系可实现钯催化的双二烯环化-捕集,在0.01%的催化剂负载量下,苯酚的TON为7.6×10 3,TOF为280 h -1,其值比通常发现的高为此和相关的碳环化。反应很好地进行规模化,并且在没有进一步优化催化剂体系或反应条件的情况下以10毫摩尔规模以优异的产率获得了反式取代的六元环产物。
Nickel and palladium complexes of enolatefunctionalised N-heterocyclic carbenes
furnishes an ionic liquid that undergoes methanolysis to crystalline 2-hydroxyethylimidazolium chloride (crystalstructure presented). Conversion to defined hydroxyethylimidazol-2-ylidene nickel complexes failed, but was accomplished with 1-methyl-3-acetophenyl-imidazolium bromide. The bis(NHC⋂O−) nickel(II) chelate is formed, rather than a methallylnickel monochelate, but with nickelocene a monochelate