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Synthesis of Functionalized 3‑Cyanoisoxazoles Using a Dianionic Reagent

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posted on 04.05.2017 by Kento Iwai, Haruyasu Asahara, Nagatoshi Nishiwaki
A series of 5-acylated 3-cyanoisoxazoles were efficiently synthesized by the Michael addition of dianionic cyano-aci-nitroacetate to α-chloro-α,β-unsaturated ketones followed by intramolecular nucleophilic substitution of the nitronate ion intermediate. In this process, the dianionic reagent serves as the safe synthetic equivalent of the explosive nitroacetonitrile. The 3-cyano group is sufficiently reactive toward ethanolysis and 1,3-dipolar cycloaddition with an azide to afford ethyl ester and tetrazole, respectively. A pyridine ring between the 5-acyl and the 4-aryl group was also constructed. This led to the formation of the isoxazolo­[5,4-c]­quinoline derivative.