Synthesis of 4-(N,N-dimethylaminomethylene)-2-alkyl-2-oxazolin-5-ones via Vilsmeier Haack reagent and their reactions with various N- and O-nucleophiles

The 4-(N,N-dimethylaminomethylene)-2-alkyl-2-oxazolin-5-ones 4 have been sy nthesised from N-acyl-alpha -amino acids 2 and methyl esters 3 with Vilsmei er-Haack reagent. The reaction of oxazolones 4a,c with primary alkylamines 7 in acetonitrile takes place at exocyclic olefinic carbon to afford substi tuted product 4-alkylaminomethylene-2-alkyl-2-oxazolin 5-ones 8, whereas th e reaction of oxazolones 4a-d with hydrazine hydrate gives cyclised product 4-acylamino-5-hydroxypyrazoles 9a-d, respectively. The methanolysis of oxa zolones 4c,d with sodium methoxide in methanol takes place at lactone carbo nyl carbon to give methyl 2-acylamino-3-dimethylaminopropenoates 12c,d. How ever, the ethanolysis with sodium ethoxide in ethanol occurrs at exocyclic carbon to afford 4-hydroxymethylene-2-oxazolin-5-ones 14c,d and N-acyl-alph a -amino acids 15c,d at room and reflux temperature, respectively.