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Synthesis PowerPoint Presentation

Synthesis

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Synthesis

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  1. Synthesis

  2. Biosynthesis Reagents = small carbon-based molecules (e.g. amino acids, carbohydrates) Catalysts = enzymes, proteins that bind and then catalyze chemical reaction

  3. Chapter 17: Aldehydes and Ketones – Nucleophilic Addition

  4. 17.1 – Nomenclature of Aldehydes and Ketones

  5. 17.2 – 17.4 – Structure of C=O and Sources

  6. 17.5 – Nucleophilic Addition Nucleophiles: H2O – hydrates H- from NaBH4 or LiAlH4 R- from RMgX, RLi NC-, ROH, RNH2, R2NH

  7. 17.6 – Hydration of Aldehydes and Ketones a Hydrate Formation (relevant to H2CrO4 oxidation) Table 17.3

  8. 17.6 – Hydration of Aldehydes and Ketones Electronic(how stable is the carbonyl – how positive is the carbon?) Steric(how crowded does the hydrate become?) Hydrate becomes more crowded, which effects the equilibrium with the precursor aldehyde or ketone

  9. 17.6 – Hydration of Aldehydes and Ketones Hydrate Formation is Base-Catalyzed Reaction faster than just with water (pH 7) Hydroxide is much more nucleophilic than water Hydroxide regenerated in second step

  10. 17.6 – Hydration of Aldehydes and Ketones

  11. 17.6 – Hydration of Aldehydes and Ketones – Fig 17.5

  12. 17.6 – Hydration of Aldehydes and Ketones Hydrate Formation is also Acid-Catalyzed Reaction faster than just H2O, H+ regenerated in second step

  13. 17.7 – Cyanohydrin Formation Both HCN and cyanide anion present in mixture Cyanide anion catalyzes the reaction, adds to the C=O New C-C bond formed (compare with Grignard)

  14. 17.8 – Acetal Formation • Acid catalyzed, use TsOH for example • Use excess ROH to drive equilibrium to the right • Water is the byproduct • Acetals are stable to bases and nucleophiles • Use excess water and H+ to go back to carbonyl - mechanism

  15. 17.8 – Acetal Formation Acetals do not react with bases or nucleophiles - useful

  16. 17.9 – Acetals as Protecting Groups Possible solution:

  17. 17.9 – Acetals as Protecting Groups

  18. 17.9 – Acetals as Protecting Groups – Hydrolysis

  19. 17.10 – Reaction with Primary Amines – Imines

  20. 17.10 – Reaction with Primary Amines – Imines opsin

  21. 17.10 – Reaction with Primary Amines – Imines

  22. 17.11 – Reaction with Secondary Amines – Enamines

  23. 17.12 – The Wittig Reaction Phosphonium salt Wittig ylide

  24. 17.12 – The Wittig Reaction

  25. 17.12 – The Wittig Reaction Retrosynthesis: Synthesis:

  26. 17.13 – Planning an Alkene Synthesis by the Wittig Reaction

  27. 17.14 – Stereoselective Addition to Carbonyls

  28. 17.15 – Oxidation of Aldehydes (via the Hydrate)

  29. 17.16 – Baeyer-Villager Oxidation of Ketones

  30. 17.16 – Baeyer-Villager Oxidation of Ketones