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Most common imides are prepared by heating dicarboxylic acids or their anhydrides and ammonia or primary amines. The result is a condensation reaction: [5] (RCO) 2 O + R′NH 2 → (RCO) 2 NR′ + H 2 O. These reactions proceed via the intermediacy of amides. The intramolecular reaction of a carboxylic acid with an amide is far faster than the ...
One plausible reaction mechanism is depicted below: [15]. Detailed Ugi mechanism. Amine 1 and ketone 2 form the imine 3 with loss of one equivalent of water. Proton exchange with carboxylic acid 4 activates the iminium ion 5 for nucleophilic addition of the isocyanide 6 with its terminal carbon atom to nitrilium ion 7.
The general structure of an imine. In organic chemistry, an imine (/ ɪ ˈ m iː n / or / ˈ ɪ m ɪ n /) is a functional group or organic compound containing a carbon–nitrogen double bond (C=N). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds.
Treatment of the resulting compound with ammonia then completes the conversion to the amidine. [1] Instead of using a Bronsted acid, Lewis acids such as aluminium trichloride promote the direct amination of nitriles, [2] or, in certain exceptional cases, of amides. [3] Dimethylformamide acetal reacts with primary amines to give amidines: [4]
The reaction is acid catalyzed and the reaction type is nucleophilic addition of the amine to the carbonyl compound followed by transfer of a proton from nitrogen to oxygen to a stable hemiaminal or carbinolamine. With primary amines, water is lost in an elimination reaction to an imine. With aryl amines, especially stable Schiff bases are formed.
The secondary amide 1 reacts via its enolized form with phosphorus pentachloride to form the oxonium ion 2. This produces a chloride ion which deprotonates the oxonium ion to form and imine 3 and hydrogen chloride. These then react with one another to form an amine, with loss of the phosphorus chloride residue.
The imine is often generated in situ from an amine and formaldehyde.An example is the reaction of cyclopentadiene with benzylamine to an aza norbornene. [9]The catalytic cycle starts with the reactions of the aromatic amine with formaldehyde to the imine and the reaction of the ketone with proline to the diene.
Compared to amines, amides are very weak bases. While the conjugate acid of an amine has a pK a of about 9.5, the conjugate acid of an amide has a pK a around −0.5. Therefore, compared to amines, amides do not have acid–base properties that are as noticeable in water. This relative lack of basicity is explained by the withdrawing of ...