Azlactones alcoholysis

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. 

This process proceeds as a DKR [13, 190] because the DMAP catalyst promotes not only the asymmetric alcoholysis of the azlactone but also its racemization under the reaction conditions the N-benzoyl a-amino acid ester product does not racemize under these conditions. Johannsen has also screened chiral DMAP 21 (Fig. 8.4) for this transformation, but obtained poorer yields and selectivities [102],... 

The azlactones usually are isolated either by coolii the reaction mixture and removing the azlactone by filtration or by pouring the cold reaction mixture into water, allowing the excess acetic mihydride to hydrolyze, and collecting the crude azlactone. The product can be. purified by recryst lization from ethanol (with the exception of a few which undei alcoholysis), benzene, petroleum ether, or ethyl acetate. 

---