formed as the corresponding O-tautomers. Slow equilibration between O- and C-enolate tautomers is observed for the nickel complex with an unsubstituted enolate function (M-O-C=CH(2)). Theoretical DFT calculations suggest that the barrier for the tautomer exchange has its origin in the rigidity of the metallacycle. Whilst the C-enolate tautomer is unreactive towards aldehydes, the corresponding O-enolate
Ni和Pd的螯合
二膦的2-酰基芳基配合物与KtBuO反应生成
金属环烯醇化物配合物。在Pd的情况下,最好通过碳原子进行配位,但形成的O-烯醇
镍镍化合物是相应的O-互变异构体。对于具有未取代的烯酸酯功能(MOC = CH(2))的
镍配合物,观察到O和C烯酸酯互变异构体之间的平衡缓慢。DFT理论计算表明,互变异构体交换的障碍源于
金属环的刚性。C-烯醇式互变异构体对醛不具有反应性,而相应的O-烯醇式添加到MeCHO和PhCHO中,产生了保留烯醇式官能团的产物。这些产物的羰基化干净地导致以高度选择性的方式形成烯醇内酯。