Alkylidene and Metalacyclic Complexes of Tungsten that Contain a Chiral Biphenoxide Ligand. Synthesis, Asymmetric Ring-Closing Metathesis, and Mechanistic Investigations
Citations Over TimeTop 10% of 2003 papers
Abstract
Two complexes that contain the racemic or enantiomerically pure (S) form of the 3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diolate (Biphen(2-)) ligand, W(NAr)(CHCMe(2)Ph)(Biphen) (2a) and W(NAr')(CHCMe(2)Ph)(Biphen) (2b) (Ar = 2,6-i-Pr(2)C(6)H(3); Ar' = 2,6-Me(2)C(6)H(3)), were prepared and shown to be viable catalysts for several representative ring-closing reactions to give products in good yields in most cases and high % ee in asymmetric reactions. Exploration of the reaction between 2a and a stoichiometric amount of one desymmetrization substrate allowed two intermediate tungstacyclobutane complexes to be observed, in addition to the final and quite stable tungstacyclobutane complex formed in a reaction between the ring-closed product and a tungsten methylene complex. Reactions involving (13)C labeled ethylene allowed for the observation of an unsubstituted tungstacyclobutane complex, an ethylene complex, an unsubstituted tungstacyclopentane complex, and a heterochiral dimeric form of a methylene complex. The tungstacyclopentane complex was found to catalyze the dimerization of ethylene to 1-butene slowly.
Related Papers
- → Metathesis of C4 olefin over Mo-based heterogeneous catalysts: A novel route to propene and isopentene(2012)19 cited
- → Desymmetrization by direct cross-metathesis producing hitherto unreachable P-stereogenic phosphine oxides(2005)31 cited
- → 4902764 Polymeric sulfide mineral depressants(1990)2 cited
- → Metathesis Reactions in Solid‐Phase Organic Synthesis(2010)2 cited
- → Nanoparticulate gold oxidation catalyst(2003)