Azlactone synthesis

Benzilic acid rearrangement Benzoin reaction (condensation) Blanc chloromethylation reaction Bouveault-Blanc reduction Bucherer hydantoin synthesis Bucherer reaction Cannizzaro reaction Claisen aldoi condensation Claisen condensation Claisen-Schmidt reaction. Clemmensen reduction Darzens glycidic ester condensation Diazoamino-aminoazo rearrangement Dieckmann reaction Diels-Alder reaction Doebner reaction Erlenmeyer azlactone synthesis Fischer indole synthesis Fischer-Speior esterification Friedel-Crafts reaction... 

Formation of 5-oxazolones (or azlactones ) (2) by intramolecular condensation of acylglycines (1) in the presence of acetic anhydride is known as the Erlenmeyer-Plochl azlactone synthesis. ... 

In 1959, Crawford and Little reported superior yields of 3 in reactions of aromatic aldehydes by using isolated, crystalline 2-phenyloxazol-5-one (2, Ri = Ph) compared to direct reaction with hippuric acid (1, Ri = Ph). An early report by Boekelheide and Schramm on the use of ketones in the Erlenmeyer azlactone synthesis includes treatment... 

Bismuth(III) acetate catalyzes the synthesis of azlactones (17) from aromatic aldehydes in moderate to good yields via the Erlenmeyer synthesis. While the standard procedure for azlactone synthesis consists of using a stoichiometric amount of fused anhydrous sodium acetate, 10 mol% of Bi(OAc)3 is sufficient to catalyze the reaction and the crude product is found to be > 98% pure. 

Modification of the Erlenmeyer reaction has been developed using imines of the carbonyl compounds, obtained with aniline," benzylamine or n-butylamine. Ivanova has also shown that an A-methylketimine is an effective reagent in the Erlenmeyer azlactone synthesis. Quantitative yield of 19 is generated by treatment of 3 equivalents of 2-phenyl-5(4ff)-oxazolone (2) (freshly prepared in benzene) with 1 equivalent of iV-methyl-diphenylmethanimine (18) in benzene. Products resulting from aminolysis (20), alkali-catalyzed hydrolysis (21), and alcoholysis (22) were also described. 

A variant of the Perkin reaction is the Erlenmeyer-Plochl-azlactone synthesis By condensation of an aromatic aldehyde 1 with an N-acyl glycine 5 in the presence of sodium acetate and acetic anhydride, an azlactone 6 is obtained via the following mechanism ... 

Erlenmeyer, E., Jr. Ann. 1893, 275, 1. Emil Erlenmeyer, Jr. (1864—1921) was bom in Heidelberg, Germany to Emil Erlenmeyer (1825—1909), a famous chemistry professor at the University of Heidelberg. He investigated the Erlenmeyer-Plochl azlactone synthesis while he was a Professor of Chemistry at Strasburg. 

Brooks, D. A. Erlenmeyer—Plochl Azlactone Synthesis in Name Reactions in Heterocyclic Chemistry, Li, J. J. Corey, E. J., Eds. Wiley Sons Hoboken, NJ, 2005, 229-233. (Review). 

Azlactone synthesis. Use of the reagent in the azlactone synthesis of amino acids is illustrated by a procedure for the preparation of DL-phenylalanine. - A mixture of 0.5 mole each of benzaldehyde, hippuric acid, and anhydrous sodium acetate is treated with 153 g. of acetic anhydride, and the mixture heated and stirred until the... 

Fig. 3 Overall sequence for azlactone synthesis, hydrogenation, and hydrolysis for the preparation of amino acids.

The enol acetates of a-keto acids can be accessed by a variation of the azlactone synthesis. They can also be reduced by Knowles catalyst, but ee values are 87-88% and the substrate to catalysis ratio needed for reduction does not allow this to be an economic approach to a-hydroxy acids although the reaction times are reduced compared with the corresponding carboxylate esters [9, 29]. 

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