A novel catalyst for the synthesis of 3–5-disubstituted isoxazole derivatives from aldoximes

Abstract

An efficient new approach has been described for the synthesis of substituted isoxazole derivatives 3a-l from substituted aldoximes and diethyl acetylenedicarboxylate using NaNO₂ and AlCl₃ in one step in moderate to excellent yields (55–94%). The key nitrile N-oxide intermediates that are required for the synthesis of isoxazole derivatives are formed by treatment of substituted aldoxime with assisted discovery of its newer applications by successive treatment with NaNO₂. The generated nitrile oxides underwent [3 + 2] dipolar cycloaddition of alkynes over AlCl₃ as a Lewis acid. Moreover, this approach has considerably assisted in the discovery of its significant advantages. This strategy is creating a five-membered ring with an oxygen and nitrogen atom adjacent to each other as either catalyst or reagent. The structures of the synthesized compounds were confirmed by spectroscopic methods, and a mechanism was proposed.

Graphical abstract