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

摘要

The4-(N,N-dimethylaminomethylene)-2-alkyl-2-oxazolin-5-ones 4 have been synthesised from N-acryl-#alpha#-amino acids 2 and methyl esters 3 with Vilsmeier-Haack reagent. The reaction of oxazolones 4a,c with primary alkylamines 7 in acetonitile takes place at exocyclic olefinic carbon to afford substituted product 4-alkylaminomehtylene-2-alkyl-2-oxazolin-5-ones 8, whereas the reaction of oxazolones 4a-d with hydriazine hydrate gives cyclised prduct 4-acylamino-5-hydroxypyrazoles 9a-d, respectively. The methanolysis of oxazolones 4c, d with sodium methoxide in methanol takes palce at lactone carbonyl carbon to give methyl 2-acylamino-3-dimethylaminopropenoates 12c, d. However, the ethanolysis with sodium ethoxide in ethanol occurrs at exocyclic carbon to afford 4-hydroxymethylene-2-oxazolin-5-ones 14c,d and N-acyl-#alpha#-amino acids 15c, d at room and reflux temperatuare, respectively.