Reductive Approach to Nitrones from N-Siloxyamides and N-Hydroxyamides

Abstract

Abstract This article describes the full details of our reductive approach to nitrones from amides. Reduction of N-siloxyamides with the Schwartz reagent [Cp2ZrHCl], followed by addition of an acid provided functionalized nitrones. The developed conditions were then extended to a catalytic version with the Vaska complex [IrCl(CO)(PPh3)2] and (Me2HSi)2O starting from N-hydroxyamides. 1H NMR studies of the Ir-catalyzed reaction revealed that the developed conditions promoted two different types of catalytic reactions including dehydrosilylation of an N-hydroxyl group and subsequent hydrosilylation of an amide carbonyl. A salient feature of our methods is their high chemoselectivity in the presence of a variety of functional groups. In addition, our reductive methods enabled concise synthesis of cyclic and macrocyclic nitrones, which are known to be challenging compounds to access by conventional methods.