Grubbs' Alkene Metathesis Flashcards
Describe the structure of the Grubbs’ (I) catalyst
Describe the structure of the Grubbs’ (II) catalyst
Ring-Closing Metathesis works for what type of ring systems?
Works for ring sizes 5 or bigger
What are the products of this reaction
- Forms a cyclic alkene and Ethene
- (is a reversible process, but ethene forms as a gas and will bubble out of solution)
What is the mechanism for the following reaction?
- Through a series of [2+2] and retro [2+2] reactions
- The Ru side-product will re-enter the catalytic cycle
What is a homo-dimer
Has the same R group on both sides of the alkene
How do we avoid a homo-dimer being formed during a cross-metathesis reaction
We need two electronically different alkenes to avoid homo-dimerisation
(i.e. R2 would have to be an EWG if R1 was an aromatic)
If R is an alkyl or aryl
The equilibrium of this reaction is….
Fast
(This reaction will simultaneously occur while the cross metathesis occurs)
What is the product of this reaction
Why does only a Trans product of the following reaction occur?
- In the square TS, the R group and the EWG are on opposite sides of the plane (opposing dipole stabilisation)
- hence a trans alkene forms
What is the mechanism for the following reaction?
- Series of [2+2] and retro [2+2]
- Last step is essentially non-reversible, which allows the dimer to build up
- The Ru by-product re-enters the catayltic cycle
What stops the homo-dimer from building up in concentration during this reaction?
- Because the reaction forming the homo-dimer are very fast and reversible
