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Weinreb and Nahm originally proposed the following reaction mechanism to explain the selectivity shown in reactions of the Weinreb–Nahm amide. Their suggestion was that the tetrahedral intermediate (A below) formed as a result of nucleophilic addition by the organometallic reagent is stabilized by chelation from the methoxy group as shown. [1]
The initial product is a thioamide for example that of acetophenone [7] which can again be hydrolyzed to the amide. The reaction is named after Karl Kindler The Kindler modification of the Willgerodt rearrangement. A possible reaction mechanism for the Kindler variation is depicted below: [8]
The Schotten–Baumann reaction is a method to synthesize amides from amines and acid chlorides: An example of a Schotten-Baumann reaction. Benzylamine reacts with acetyl chloride under Schotten-Baumann conditions to form N-benzylacetamide. Schotten–Baumann reaction also refers to the conversion of acid chloride to esters.
In one variation called the Darapsky degradation, [19] or Darapsky synthesis, a Curtius rearrangement takes place as one of the steps in the conversion of an α-cyanoester to an amino acid. Hydrazine is used to convert the ester to an acylhydrazine, which is reacted with nitrous acid to give the acyl azide. Heating the azide in ethanol yields ...
Attack by water converts 6 to protonated imidic acid 7, which undergoes loss of proton to arrive at the imidic acid tautomer of the final amide. In an alternative mechanism, the migration occurs at 9, directly after protonation of intermediate 3, in a manner similar to the Baeyer–Villiger oxidation to give protonated amide 10. Loss of a ...
Ammonium formate is a source of formic acid and ammonia. Starting with nucleophilic attack on the carbonyl by the ammonia, the carbonyl is converted to the iminium ion: [6] NH 4 HCO 2 ⇌ NH 3 + HCO 2 H NH 3 + R 2 C=O + HCO 2 H → R 2 C=NH + 2 + HCO − 2. The iminium is then reduced by the formate: R 2 C=NH + 2 + HCO − 2 → R 2 CH−NH 2 ...
The reaction mechanism involves the acylation and activation of the acid 1 to the mixed anhydride 3. The amide will serve as a nucleophile for the cyclization forming the azlactone 4. Deprotonation and acylation of the azlactone forms the key carbon-carbon bond. Subsequent ring-opening of 6 and decarboxylation give the final keto-amide product ...
The archetypal Beckmann rearrangement [4] is the conversion of cyclohexanone to caprolactam via the oxime. Caprolactam is the feedstock in the production of Nylon 6. [5] The Beckmann solution consists of acetic acid, hydrochloric acid and acetic anhydride, and was widely used to catalyze the rearrangement