A Cascade Process of Hydroxamates Renders 1,6-Dioxa-3,9-diazaspiro[4.4]nonane-2,8-diones

Abstract

A cascade route to 1,6-dioxa-3,9-diazaspiro[4.4]nonane-2,8-diones from N,O-diacyl hydroxylamines consisting of a two-step procedure is described. The key transformation is a [3,3]-sigmatropic rearrangement of N,O-diacyl hydroxylamines promoted by formation of a silylketenaminal followed by an intramolecular cyclization and a final spirocyclization. The optimum reaction conditions employ a one-fold excess of each reagent and are utilized to prepare a range of structurally diverse examples of this class of compound.