A Palladium-Catalyzed Strategy for the Preparation of Enantioenriched Lactams
Résumé
Lactams are ubiquitous in biologically active natural products or pharmaceuticals and prompted organic chemists to involve practical synthetic equivalents of the highly desired {C–C(=O)–N} synthon in cycloaddition reactions. In this context, α-haloamides have been extensively described as versatile precursors of this important synthon but, despite a myriad of known synthetic methodologies [1], asymmetric cycloadditions of these substrates are scarce [2] and a general strategy to access enantioenriched cycloadducts would be of high importance. Our research group is interested in catalytic cycloadditions involving π-allylpalladium zwitterionic dipoles [3-5]. We have recently identified original vinyloxazolidine-2,4-diones as competent synthetic equivalents of the {C–C(=O)–N} synthon. Under Pd(0) catalysis, the resulting π-allylpalladium(II) intermediates can act as aza-1,3-dipoles in (3+2) cycloadditions towards enantioenriched lactams.