Synthesis of Imines
Imines are typically prepared by the condensation of primary amines and aldehydes and less commonly ketones. In terms of mechanism, such reactions proceed via the nucleophilic addition giving a hemiaminal -C(OH)(NHR)- intermediate, followed by an elimination of water to yield the imine. (see alkylimino-de-oxo-bisubstitution for a detailed mechanism) The equilibrium in this reaction usually favors of the carbonyl compound and amine, so that azeotropic distillation or use of a dehydrating agent such as molecular sieves is required to push the reaction in favor of imine formation.
Several other methods exist for the synthesis of imines.
- Condensation of carbon acids with nitroso compounds.
- The rearrangement of trityl N-haloamines in the Stieglitz rearrangement.
- Dehydration of hemiaminals.
- By reaction of alkenes with hydrazoic acid in the Schmidt reaction.
- By reaction of a nitrile, hydrochloric acid and an arene in the Hoesch reaction.
- Multicomponent synthesis of 3-thiazolines in the Asinger reaction.
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