Nucleophilic Neighboring Group Participation

Nucleophilic Neighboring Group Participation PowerPoint PPT Presentation


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Nucleophilic Neighboring Group Participation. Case I: Rationale. Nucleophilic NGP. Case II. Nucleophilic NGP. Case III. ?Non-nucleophilic" NGP. Acetolysis of Phenyl tosylates. Possible explanations for the results of the acetolysis reactions. Direct bimolecular nucleophilic attack at C-2Inconsistent with the experimental data. Why?Formation of a secondary carbocation at C-2Inconsistent with the experimental data. Why?.

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Nucleophilic Neighboring Group Participation

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1. Nucleophilic Neighboring Group Participation

2. Nucleophilic Neighboring Group Participation Case I: Rationale

3. Nucleophilic NGP Case II

4. Nucleophilic NGP Case III

5. “Non-nucleophilic” NGP Acetolysis of Phenyl tosylates

6. Possible explanations for the results of the acetolysis reactions Direct bimolecular nucleophilic attack at C-2 Inconsistent with the experimental data. Why? Formation of a secondary carbocation at C-2 Inconsistent with the experimental data. Why?

7. Rapidly equilibrating secondary carbocations to account for the acetolysis results? The “Windshield-Wiper” Effect

8. Additional data concerning acetolysis of phenyl tosylates Fact One - Scrambling of a label

9. Additional data concerning acetolysis of phenyl tosylates Fact Two - Substituent effects

10. Additional data concerning acetolysis of phenyl tosylates Fact Three - Formation of Spirane products

11. Additional data concerning acetolysis of phenyl tosylates Fact Four - Unusual Kinetics

12. Explanation to account for the acetolysis results Phenonium ion participation

13. Alkyl Participation ? - bridged complexes

14. Corroborating evidence for alkyl participation

15. Open carbocation possibility

16. Methyl bridged intermediate

17. Data for the solvolysis of cyclohexyl tosylates

18. Rationale for cyclohexyl tosylate solvolysis

19. Rationale for cyclohexyl tosylate solvolysis cont’d. ?-Hydrogen participation

20. Solvolysis of unsaturated tosylates

21. Possible explanations for solvolysis of unsaturated tosylates

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