Diastereo- and Enantioselective (3 + 2) Cycloaddition of a New Aza-π-Allylpalladium Zwitterionic Intermediate.

Cycloaddition of azaoxyallyl cations or other C─(C═O)─N synthon precursors is a well-established route toward lactams and other -heterocycles, but despite the wide synthetic scope of this approach, enantioselective versions remain scarce. We herein report 5-vinyloxazolidine-2,4-diones (VOxD) as a suitable precursor of a new palladium-π-allylpalladium intermediate. In the presence of electrophilic alkenes, (3 + 2) γ-lactam cycloadducts could be formed with a high level of diastereo- and enantioselectivity.

Vinylcyclopropanes as All-Carbon 1,5-Dipoles: A Reactivity Switch for Palladium-Catalyzed (5 + 4) Cycloadditions.

Azonanes were prepared by a palladium-catalyzed (5 + 4) cycloaddition between activated vinylcyclopropanes and 1-azadienes. During this process, the vinylcyclopropane partner displayed an unusual reactivity and behaved as an all-carbon 1,5-dipole. A ,-bidentate ligand was required to inhibit the formation of thermodynamic (3 + 2) cycloadducts.