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MANNICH REACTION

MANNICH REACTION. ketone. formaldehyde. excess. . pH 6-8. -. Cl. -. . iminium salt. A variety of R groups may be used. Mannich Base “Schiff’s Base”. Aldehydes other than formaldehyde may be used. The reaction works best with methyl ketones.

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MANNICH REACTION

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  1. MANNICH REACTION ketone formaldehyde excess .. pH 6-8 - Cl - .. iminium salt A variety of R groups may be used Mannich Base “Schiff’s Base” Aldehydes other than formaldehyde may be used. The reaction works best with methyl ketones. Et2NH - HCl is generally used in excess, hence the chloride counter ion. Other secondary amines sometimes work in place of diethylamine.

  2. Activated phenols will also give a reaction similar to the Mannich Condensation. + + - .. Mannich Base resonance structures AROMATIC SUBSTITUTION + This is essentially an electrophilic aromatic substitution reaction – a hydrogen on the ring is replaced by the Mannich Base which is an electrophile. Phenols with activating substituents (methoxy, hydroxy, amino) can give this reaction.

  3. + : : _ .. + .. HNEt2 Mannich Base B: H+

  4. PICTET-SPENGLER REACTION condensation occurs at biological pH values H3O+/D + a tetrahydroisoquinoline ring Mannich Base if cyclization does not occur sponttaneously This is a general method for the synthesis of tetrahydroisoquinoline rings.

  5. BISCHLER-NAPIERALSKI REACTION amide H3PO4 or P2O5 via - H2O synthesis of the initial amide Intermediate loses water Synthesis of a dihydroisoquinoline An acid anhydride may be used instead of an acid chloride to synthesize the amide.

  6. ester-amide (urethane) .. .. H3PO4 or P2O5 H+ H+ ethyl chloroformate synthesis of the initial urethane

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