Process for the stereoselective synthesis of the E isomer of aryl alkyl oximes

摘要

Mixtures of the E and Z isomers of aryl alkyl oximes are converted to 98% or greater E isomer by a process comprising treating a solution of a mixture of E and Z isomers in an organic solvent with a protic or Lewis acid, under anhydrous conditions, to precipitate 98% pure E isomer of an immonium complex and neutralizing the precipitate with an excess of dilute organic/inorganic base, such as Na₂CO₃ or NaHCO₃. The E isomer of the ketoxime is precursor for highly insecticidal ketoximinoethers.