Lecture 5:  Catalyst design and properties of common ligands

Lecture 5: Catalyst design and properties of common ligands PowerPoint PPT Presentation


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Lecture 5: Catalyst design and properties of common ligands

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1. Lecture 5: Catalyst design and properties of common ligands

2. Catalyst initiation How do we get Pd(0)? Pd(0) sources Pd(II) sources

3. Catalyst initiation How do we get Pd(II) to Pd(0)? 1) 2)

4. Catalyst initiation 3) 4)

5. Catalyst designs Good catalyst design: Easily lose ligands Less electrons More reactive

6. Catalyst designs Large ligands can be used to prevent binding of too many ligands Ex:

7. Early ligand designs Low reactivity of aryl chlorides attributed to strength of C–Cl bond Ph–Cl = 95 kcal/mol; Ph–Br = 80 kcal/mol; Ph–I = 65 kcal/mol. More electron rich ligand would be more prone to oxidative addition

8. Early ligand designs

9. Literature Precedent

10. Alkyl phosphines useful for Suzuki

11. Reactivity with PtBu3 Very low catalyst loading possible 0.005 % Pd, 0.012 % PtBu3 Inert to aryl triflates Steric demand leads to ready access to a key palladium monophosphine complex Leads to high reactivity TON ~ 10000

12. Selectivity with PCy3 Triflates are much more reactive with PCy3 than PtBu3 Typical order of cross couplings is I > Br ~ OTf >> Cl

13. Examples of ligands SIMes Large buried volume Easily prepared and isolated

14. Examples of ligands SIPr Even larger buried volume

15. Examples of ligands IBiox Increased volume without tert-butyl group pushing into metal

16. Buchwald Ligands R2 ? H Prevents cyclometallation

17. Buchwald Ligands

18. Examples of Buchwald Ligands

19. Preparation of Buchwald Ligands

20. Cyclometallation

21. Reactivity of Buchwald Ligands

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