Search results
Results from the WOW.Com Content Network
Hippuric acid, the benzamide derivative of glycine, cyclizes in the presence of acetic anhydride, condensing to give 2-phenyl-oxazolone. [3] This intermediate also has two acidic protons and reacts with benzaldehyde, acetic anhydride and sodium acetate to a so-called azlactone. This compound on reduction gives access to phenylalanine. [4]
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.
All of the processes of Shiina macrolactonization consist of reversible reactions, with the exception of the last cyclization step.At the first stage of the reaction, mixed anhydride (MA) is produced quickly under mild conditions; at the second stage, a faster cyclization of the MA prevents an increase in MA concentration.
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH 3 CO) 2 O. Commonly abbreviated Ac 2 O , it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis .
Like straight-chained esters, the hydrolysis-condensation reaction of lactones is a reversible reaction, with an equilibrium. However, the equilibrium constant of the hydrolysis reaction of the lactone is lower than that of the straight-chained ester i.e. the products (hydroxyacids) are less favored in the case of the lactones.
The following figure shows the reaction mechanism: [2] Reaktionsmechanismus Albright-Goldman-Oxidation. First, dimethyl sulfoxide (1) reacts with acetic anhydride to form a sulfonium ion. It reacts with the primary alcohol in an addition reaction. Furthermore, acetic acid is cleaved, so that intermediate 2 is formed. The latter reacts upon ...
The mechanism of the Pummerer rearrangement begins with the acylation of the sulfoxide (resonance structures 1 and 2) by acetic anhydride to give 3, with acetate as byproduct. . The acetate then acts as a catalyst to induce an elimination reaction to produce the cationic-thial structure 4, with acetic acid as byprod
In this process the racemic lactone reacts in aminolysis with (S)-methylbenzylamine assisted by triethylaluminum to a diastereomeric pair of amides which can be separated by column chromatography. The S-enantiomer is converted back to the S-lactone in two steps by hydrolysis with potassium hydroxide and ethylene glycol followed by azeotropic ...