Synthesis

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Synthesis
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Biosynthesis
Reagents small carbon-based molecules (e.g.
amino acids, carbohydrates) Catalysts enzymes,
proteins that bind and then catalyze chemical
reaction
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Chapter 17 Aldehydes and Ketones Nucleophilic
Addition
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17.1 Nomenclature of Aldehydes and Ketones
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17.2 17.4 Structure of CO and Sources
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17.5 Nucleophilic Addition
Nucleophiles H2O hydrates H- from NaBH4 or
LiAlH4 R- from RMgX, RLi NC-, ROH, RNH2, R2NH
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17.6 Hydration of Aldehydes and Ketones
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Hydrate Formation (relevant to H2CrO4
oxidation) Table 17.3
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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
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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
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17.6 Hydration of Aldehydes and Ketones
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17.6 Hydration of Aldehydes and Ketones Fig
17.5
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17.6 Hydration of Aldehydes and Ketones
Hydrate Formation is also Acid-Catalyzed
Reaction faster than just H2O, H regenerated in
second step
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17.7 Cyanohydrin Formation
Both HCN and cyanide anion present in
mixture Cyanide anion catalyzes the reaction,
adds to the CO New C-C bond formed (compare with
Grignard)
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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

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17.8 Acetal Formation
Acetals do not react with bases or nucleophiles -
useful
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17.9 Acetals as Protecting Groups
Possible solution
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17.9 Acetals as Protecting Groups
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17.9 Acetals as Protecting Groups Hydrolysis
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17.10 Reaction with Primary Amines Imines
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17.10 Reaction with Primary Amines Imines
opsin
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17.10 Reaction with Primary Amines Imines
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17.11 Reaction with Secondary Amines Enamines
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17.12 The Wittig Reaction
Phosphonium salt Wittig ylide
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17.12 The Wittig Reaction
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17.12 The Wittig Reaction
Retrosynthesis
Synthesis
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17.13 Planning an Alkene Synthesis by the
Wittig Reaction
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17.14 Stereoselective Addition to Carbonyls
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17.15 Oxidation of Aldehydes (via the Hydrate)
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17.16 Baeyer-Villager Oxidation of Ketones
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17.16 Baeyer-Villager Oxidation of Ketones