Redox agents

Redox agents思维导图，包括：Oxidation、Reduction、summary等内容。希望对你有所帮助。

Redox agents

• Oxidation
  • Substrate discrimination
    • primary alcohol
      • aldehyde
        • carboxylic acid
    • Secondary alcohol
      • ketone
    • Tertiary alcohol
      • no reaction
    • phenol
      • quinones
    • ketone
      • no reaction
    • Aldehyde
      • carboxylic acid
  • KMnO4
    • Oxidation of substituted alkyl benzene to benzoic acid
      • only for 1', 2' alkyl groups
      • replace alkyl group by carboxylic acid generate substituted benzoic acid
    • oxidize aldehyde into carboxylic acid
  • Hot HNO3
    • oxidize aldehyde into carboxylic acid
    • also can oxidlze alcohol into acid
  • Cr(VI) reagents
    • CrO3
      • usually in aqueous acid
      • Oxidation of a primary alcohol to a carboxylic acid
        • the aldehyde is a intermediate, but can't isolated
        • the oxidation is too quik
      • oxidize secondary alcohol to ketone
      • oxidize aldehyde to carboxylic acid
    • Na2Cr2O7
      • in aqueous acetic acid
      • inexpensive
        • for large scale oxidation
      • Oxidation of substituted alkyl benzene to benzoic acid
        • only for 1', 2' alkyl groups
        • replace alkyl group by carboxylic acid generate substituted benzoic acid
      • oxidize primary alcohol into aldehyde
      • oxidize seconary alcohol into ketone
  • Dess-Martin periodinane
    • usually in dichloromethane solvent
      • Non acidic, at lower room temperature
    • oxidize primary alcohol into aldehyde
    • oxidize seconary alcohol into ketone
  • Fremy's salt
    • (KSO3)2 NO
    • oxydize phenol/hydroquinones to quinones
      • this like ubiquinones in biological system
        • coenzyme Q
        • electron stransfer
  • Common mechanism
    • laboratory
      • alcohol
        • closely related to E2
          • first is the oxidant substites H of hydroxyl group
          • then generates a C=O by elimination of intermediate, leaving group is a reduced iodine (DMP) or metcal (Cr)
            • therefore require at least one H attach to the hydroxyl attached carbon
      • aldehyde
        • through intermediate 1,1 diol/ hyrates
          • formed by hydration of aldehyde
            • equilibrium amount
          • then hydrate is oxidized through the alcohol mechanism
            • therefore require at least one H attach to the carnonyl carbon
            • the 1,1 diol produced by ketone hydration do not have more H attached on the hydroxyl attached carbon..
      • phenol
        • radical
    • NAD+/NADP+
      • 1.a base removes -OH proton
      • 2. alkoxide ion transfers a hydride ion to coenzyme
      • ps: addition accors exclusively on the Re face of the NAD+ ring
        • adding a hydrogen with pro-R geometry
  • weak oxidants
    • Ag+
    • Cu2+
  • Br2
    • like industrial oxidize aldose into aldonic acid
• Reduction
  • Mechanism
    • generally nucleophilic attack of H:-
      • nucleophilic addition
        • then protonation
          • for aldehydes/ketones
      • first nucleophilic acyl substitution
        • for acyl derivatives
          • to yield aldehyes/ketone intermediate/product
            • aldehydes often immediately oxidized to alcohol by nucleophilic addition
              • ex. LiAlH4
              • exept DIBAH
                • partial reduction
    • detailed different
      • section 14.6
      • chapter 16
        • 16.6
        • 16.8
      • 13.3
  • LiAlH4
    • much more reactive than NaBH4
      • grayish powder
        • Only soluble in ether and tetrahydrofuran
          • react violently with water
      • dangerous
        • decompose and explode when heated above 120
    • reduction of aldehyde and ketones to alcohol
    • But can also reduce carboxylic acids and esters to alcohol
      • therefore LiAlH4 cover reduction of all carbonyl groups
      • unisolatable aldehyde intermediate
      • in ether solvent
      • should followed by protonation
    • Reduce nitriles to amines
      • Through amide intermediate
        • p 626
    • Reduce amide to amines
  • NaBH4
    • safety, easy handling
      • use in either water/alcohol solution
      • white, crystalline solid
        • can weighed in the open atmosphere
    • reduction of aldehyde and ketones to alcohol
    • reduce quinones to hyroqyinones
    • Reductive amination
      • aldehyde or ketone is treated with and amine in the presence of a reducing agent NaBH4
    • similar SnCl2
  • DIBAH
    • Diisobutylaluminum hydride
    • partially reduce an ester/thioester/acylphosphate to aldehyde
      • laboratory scale method
    • interestingly, it can't partially reduce carboxylic acids..
      • no one can partially reduce acids?
        • Yes, it's all or nothing
    • at -78℃ to avoid further reduction
    • in toluene solvent
  • NADH/NADPH
    • biological system..
    • can partially reduce thioester/acylphosphate to aldehyde
  • Grignard reagents
    • work as R:-
      • reduce ketone, aldehyde, acyl derivatives, even CO2---carboxylation produce carboxylate acids
    • can't stop at ketone/ aldehyde phase when reduce acyl derivatives, usually gives 2 identical substituted tertirary alcohol
      • Use R2CuLi can substitude only onece
        • But only effective for acid chloride!
        • also usful for conjugate addition of alkyl group
    • in polar aprotic solvent ether/THF
    • production
      • 1°/2°/3° alkyl, alkenyl, aryl halide + Mg in ether or THF(polar aprotic solvent)
  • Ctalytic hydrogenation
    • H2 with pt catalyst
      • strong reduction forces reduce C=C(not aromatic), C=O(also nirtiles), and -NO2
        • double bonds are most reactive over catalytic hydrogenation
          • no aromatic
        • under normal strength, C=O in ester, aldehyde, ketone is untouched
          • less reactive
      • Mechanism
        • Syn stereochemistry addition
    • Lindar catalyst
      • reduce alkyne to alkene with syn stereochemistry
• summary
  • oxidize
    • with out limit
      • KmnO4
      • HNO3
      • all steps
        • CrO3
    • one step(stop at aldehyde)
      • Dess-Martin periodinane
      • Na2Cr2O7
        • for large scale
    • special
      • fremy's salt
    • very weak oxidants only oxidize aldehyde: reducing sugar
      • Ag+, Cu2+
        • mechanism
          • probably must through enolateion intermediate
      • Br2
  • reduce
    • all steps
      • LiAlH4
        • dangerous
      • NAD(P)H
    • one step(stop at aldehyde)
      • DIBAH
      • NAD(P)H
      • but only work for some acyl dirivatives
        • ester
        • thioester
        • acylphosphate
    • only from second step(only from aldehyde/ketone)
      • NaBH4
        • easy to handle