[(NHC)(NHCewg)RuCl2(CHPh)] Complexes with Modified NHCewg Ligands for Efficient Ring-Closing Metathesis Leading to Tetrasubstituted Olefins
作者:Volodymyr Sashuk、Lars H. Peeck、Herbert Plenio
DOI:10.1002/chem.200903275
日期:2010.4.6
yield from the ruthenium precursor. To learn which one of the two NHC ligands acts as the leaving group in olefin metathesis reactions two complexes, [(FL‐NHC)(NHCewg)RuCl2(CHPh)] and [(FL‐NHCewg)(NHC)RuCl2(CHPh)], with a dansyl fluorophore (FL)‐tagged electron‐rich NHC ligand (FL‐NHC) and an electron‐deficient NHC ligand (FL‐NHCewg) were prepared. The fluorescence of the dansyl fluorophore is quenched
咪唑鎓盐(NHC EWG ⋅ HCl中)与在4,5位上的电子可变取代基(H,H或Cl,Cl或H,NO 2或CN,CN)和位可变取代基的1,3-位(ME ,Me或Et,Et或i Pr,i Pr或Me,i Pr)被合成并转化为各自的[AgI(NHC)ewg ]配合物。[(NHC)RuCl 2(CHPh)(py)2 ]与[AgI(NHC ewg)]配合物的反应提供了各自的[(NHC)(NHC ewg)RuCl 2(CHPh)]络合物,收率极高。研究了此类络合物在开环复分解(RCM)反应中产生四取代烯烃的催化活性。为了获得定量的底物转化率,催化剂在80°C下甲苯中的催化剂负载量为0.2–0.5 mol%就足够了。在此类RCM反应中具有最佳催化活性和最快引发速率的配合物具有NHC ewg基团,该基团带有1,3-Me,i Pr和4,5-Cl,Cl取代基,可以从该化合物中以95%的分离产率合成钌前体。要