Access to the syntheses of sydnonyl-substituted α,β-unsaturated ketones and 1,3-dihydro-indol-2-ones by modified Knoevenagel reaction

A convenient method for the preparation of sydnonyl-substituted α, β-unsaturated ketones, based on Knoevenagel condensation, is presented. Although well known, this reaction has never been utilized in the condensation involving sydnone derivatives. Thus, 3-aryl-4-formylsydnones () are reacted with active methylene compounds such as acetylacetone (), ethyl acetoacetate (), diethyl malonate (), malononitrile (), ethyl cyanoacetate () and cyanoacetamide () by modified Knoevenagel condensation to afford multifunctional derivatives. Also, sydnonyl-substituted 1,3-dihydro-indol-2-one derivatives were synthesized successfully by condensing 3-aryl-4-formylsydnones () with oxindoles .