A new synthetic access to N-alkylated nitrones through Lewis acid-catalyzed conjugate additions of aldoximes

In the presence of Lewis acid catalysts, aldoximes react with alpha,beta -unsaturated carbonyl compounds at room temperature to give N-alkylnitrones in good yields. Combination of two Lewis acid catalysts, zinc(II) iodide/boron trifluoride etherate (50 mol%/50 mol%), is the best choice to mediate the reactions producing N-alkylated nitrones in excellent yields. In this procedure, a variety of aldoximes and alpha,beta -unsaturated carbonyl acceptors can be employed. (C) 2001 Elsevier Science Ltd. All rights reserved.