246047-72-3C1CCC(P(C2CCCCC2)C2CCCCC2)CC1.Cc1cc(C)c(N2CCN(c3c(C)cc(C)cc3C)[C]2=[Ru]([Cl])([Cl])=[CH]c2ccccc2)c(C)c1FCDPQMAOJARMTG-UHFFFAOYSA-LSee other relationships...
DescriptionGrubbs catalysts are a series of transition metal carbene complexes used as catalyst for olefin metathesis.1 The Grubbs catalysts are based on a ruthenium atom surrounded by five ligands: two neutral electron-donating entities (e.g., trialkylphosphines, N-heterocyclic carbenes), two monoanionic groups (e.g., halides), and one alkylidene moiety (e.g., unsubstituted and substituted methylidenes). L2X2Ru=CHR complexes (where L is a phosphine ligand) were discovered first and are referred to as the first-generation Grubbs catalyst. (L)(L’)X2Ru=CHR complexes (where L is a phosphine ligand and L’ a saturated N-heterocyclic carbene or NHC ligand) are referred to as the second-generation Grubbs catalysts. The first-generation Grubbs catalysts show attractive functional-group tolerance and handling properties and have been widely used as highly efficient promoters for ring opening metathesis polymerizations, ring-closing metathesis reactions to make disubstituted olefins, ethenolysis (i.e., cleavage of the carbon–carbon double bond), cross-metathesis of terminal olefins, and the preparation of 1,3-dienes via enyne metathesis. These catalysts and analogues are still widely used in important processes, including the ethenolysis of feedstocks derived from bio-renewable seed oils and the manufacture of macrocyclic hepatitis C therapeutics. Nevertheless, the first-generation Grubbs catalysts show limitations with electron-poor and electron-rich double bonds as well as with sterically hindered systems. The second-generation Grubbs catalysts with excellent metathesis activity while retaining the handling characteristics and broad functional-group tolerance of the earlier Grubbs catalysts are thereby developed. At the same time, the second-generation catalysts are stable against moisture and air.
Usessuzuki reaction
UsesGrubbs Catalyst M204 can be used as a catalyst for ring-closing metathesis (RCM), cross-metathesis, and ring-opening metathesis polymerization (ROMP). It is also used to synthesize trisubstituted olefins with excellent functional group tolerance and selectivity via cross-metathesis and ring closing metathesis reactions.It can also be used as a catalyst:To synthesize coumarins from phenolic compounds via RCM.To cleave secondary (E)-allyl vic-diols to aldehydes.
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246047-72-3DTXSID901014845PreparationGrubbs and co-workers reported a direct approach towards the preparation of the 4,5-dihydroimidazol-2-ylidene-substituted ruthenium-based catalysts. Compared to their predecessor, Grubbs catalyst 2nd generation display higher reactivity, better stability, and improved functional group tolerance.[3]
DefinitionAdlhart and Chen found that ligand rotation is the difference between the activity of the first and second-generation Grubbs catalysts. This difference is brought about by a difference in the symmetry of the ligands. The phosphine ligand has a threefold symmetry, which causes a high barrier in the middle of the reaction coordinate, which is forced by the need for rotation of the phosphine. However, the barrier is absent for the second-generation Grubbs catalyst, with twofold symmetry of the NHC ligand. The rate-limiting step for second-generation catalysts is always phosphine dissociation[2].