Synthesis Using Pyridinium N -Ylides. I. Synthesis and Some Reactions of Substituted 1-(Acetylimino)pyridinium Ylides

Abstract

Pyridinium N-imines reacted smoothly with diethyl malonate and ethyl cyanoacetate in ethanol at room temperature to give the corresponding 1-(ethoxycarbonylacetylimino)- and 1-(cyanoacetylimino)pyridinium ylides in 59–87% yields. These ylides were converted to 1-(acetylimino)pyridinium ylide derivatives by the treatment with acetic anhydride. The alkaline treatment of the pyridinium salts which were prepared by the alkylation of the N-ylides with alkyl halides, gave the corresponding 3-ethoxycarbonyl- and 3-cyano-1,2-dihydropyrazolo-[1,5-a]pyridin-2-one derivatives in 8–51% yields.