Erlenmeyer reaction

Erlenmeyer reaction is the condensation of aromatic aldehydes with hippuric acid to form aziactones (important intermediates in the preparation of amino- and keto-acids)... 

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. 

Several improved methods for the preparation of known unsaturated azlactones as well as some interesting new compounds of this type have been reported. Crawford and Little observed that the direct use of 2-phenyl-5-oxazolone (1) in the Erlenmeyer reaction gave much improved yields (35-74%) of unsaturated azlactones with aliphatic aldehydes and with ketones such as acetone and cyclohexanone [Eq, (1)], The usual procedure of mixing a carbonyl compound, hippuric acid, acetic anhydride, and sodium (or lead) acetate affords poor yields in the aliphatic series. 

There are four possible classes of bis-5(4H)-oxazolones (cf. 8-11). Compounds of type 8 may be prepared by the Erlenmeyer reaction on dialdehydes. The compound in which R is derived from the 4,4 -dialdehyde of diphenyl ether (R = CgHs) is a recent example. ... 

Mechanistic studies of the Erlenmeyer reaction suggest that the reaction proceeds through initial rapid and reversible formation of the saturated oxazolone followed by an aldol condensation of the latter with the carbonyl compound and subsequent dehydration. ... 

Other amino acid precursors have been used as starting materials in the Erlenmeyer reaction. A classical reaction of oxazolones is ring opening to give dehydroamino acid derivatives but there are a number of examples when the reverse reaction has been exploited including cyclizations of A-benzoyl-a,p-dehydrophen-ylalanine," a-(acetylamino)cinnamic esters," and 2-(acylamino)-2-alkenamides (Scheme 7.118)." ... 

The Erlenmeyer reaction has also been used to prepare new 4-arylmethylene-2-[3-chlorobenzo[Z ]thien-2-yl]-5(4//)-oxazolones 800 from the appropriate A-acylgly-cine 799 and several aldehydes (Scheme 7.244). °° The pharmacological activity of these compounds as antibacterial and antiinflamatory agents has been studied. 

In Approach (B), aniline is converted into the corresponding nitrogen mustard, which is formylated to the benzaldehyde nitrogen mustard V. The alanine moiety is constructed via the Erlenmeyer reaction with hippuric acid, reduction, and hydrolysis [23,34—38]. 

Ivanova, G. A modification of the Ploechl-Erlenmeyer reaction. I. Synthesis of 2-phenyl-4-diphenylmethylene-5(4H)-oxazolone. Tetrahedron 1992,48, 177-186. 

Diaz, J. L., Villacampa, B., Lopez-Calahorra, F., Velasco, D. Synthesis of polyconjugated carbazolyl-oxazolones by a tandem hydrozirconation-Erlenmeyer reaction. Study of their hyperpolarizability values. Tetrahedron Lett. 2002, 43, 4333-4337. 

Erlenmeyer reaction The condensation reaction between an aromatic aldehyde and an A-acyl derivative of glycine, in the presence of acetic anhydride and sodium acetate, to give an azlactone. Erythro isomer The stereoisomer of CabxC.lby that is represented by the following diagram using... 

A gentle suction is applied to draw the gas in the desired direction. (A) Bunsen burner. (B) Sample. (C) Wide mouth Erlenmeyer reaction flask. (D) HCl reservoir. (E) Drying tube filled with Ascarite (NaOH on asbestos) to remove CO. ... 

With the same kind of molecule and the same method of synthesis, 4-arylidene-2-phenyl-5(41-f)-oxazolones were synthesized by the Erlenmeyer reaction from aromatic aldehydes and hippuric acid using calcium acetate under solvent-free conditions (Eq. 27) [113] ... 

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