Heterocyclization Reactions of 3-methylisoxazol-5-amine with Pyruvic Acid Derivatives Using Classical and Non-classical Methods of Activation

 Two- and multicomponent interactions between 3-methylisoxazol-5-amine and pyruvic acid derivatives were studied both by using classical methods of activation, as well as under microwave irradiation and ultrasonication. It was shown that the reactions with esters of arylidene pyruvic acids could lead to the formation of three different types of heterocyclic systems, while in the case of arylidene pyruvic acid a very insignificant conversion of the starting compounds to isoxazolo[5,4-b]pyridine carboxylic acids was observed, due to the low stability of 3-methylisoxazol-5-amine.