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Aromatic Amines

Aromatic Amines. Recall: The amino group is a powerful activating group that directs ortho and para. Reduction of Nitro Compounds. Catalytic hydrogenation: Reduction with finely divided metal powders:. 23.11 Synthesis of Amines. Reduction of Nitro Compounds.

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Aromatic Amines

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  1. Aromatic Amines • Recall: • The amino group is a powerful activating group that directs ortho and para

  2. Reduction of Nitro Compounds • Catalytic hydrogenation: • Reduction with finely divided metal powders: 23.11 Synthesis of Amines

  3. Reduction of Nitro Compounds • LiAlH4 and NaBH4 fail to provide the amine 23.11 Synthesis of Amines

  4. Problems • Draw the products for the following reactions:

  5. Reductive Amination

  6. Sodium cyanoborohydride, NaBH3CN and sodium triacetoxyborohydride, NaBH(OAc)3, are common choices in the lab for the reduction step

  7. Formaldehyde can be used to introduce methyl groups

  8. 23.7 Alkylation and Acylation Reactions of Amines

  9. Problem • Draw the complete mechanism for the following problem:

  10. Hofmann and Curtius Rearrangements

  11. The Hofmann Rearrangement • Sometimes called the Hofmann hypobromite reaction • Cl2 is sometimes used in place of Br2 • A primary amide is the required starting compound 23.11 Synthesis of Amines

  12. The Curtius Rearrangement • Acyl azides provide access to primary amines via an isocyanate • Concerted reaction

  13. The Curtius Rearrangement • The resulting isocyanate can be hydrated in acid or base • Carbamic acids spontaneously decarboxylate 23.11 Synthesis of Amines

  14. Hofmann vs. Curtius • In the Hofmann rearrangement, the isocyanate cannot be isolated as the reaction is carried out in aqueous base 23.11 Synthesis of Amines

  15. Curtius and Hofmann Rearrangements • In both of these reactions, the alkyl group migrates with complete retention of configuration 23.11 Synthesis of Amines

  16. Problems • Draw the mechanisms for the following rxns

  17. Acylation of Amines • Amines can be converted into amides by reaction with acid chlorides, anhydrides, or esters.

  18. See section 21.8 for review of these rxns

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