Base‐catalyzed [3 + 2]/[4 + 2]‐annulations of cyclic N‐sulfimines with γ‐ and δ‐sulfonamido/hydroxy‐α,β‐unsaturated carbonyls: Stereoselective synthesis of imidazolidines, oxazolidines, hexahydropyrimidines, and 1,3‐oxazinanes

A highly efficient and straightforward synthetic methodology has been established for the preparation of imidazolidine derivatives through the [3 + 2]‐annulation of cyclic N‐sulfimines. This reaction involves the reaction of cyclic N‐sulfimines and γ‐sulfonamido‐α,β‐unsaturated carbonyl compounds, with Cs2CO3 serving as the catalyst. The outcome is a diverse range of imidazolidine derivatives with remarkable yields and stereoselectivities. In addition, the [4 + 2]‐annulation between cyclic N‐sulfimines and δ‐sulfonamido‐α,β‐unsaturated carbonyl compounds, catalyzed by Et3N, has been successfully applied for the synthesis of stereoselective hexahydropyrimidines. Furthermore, the base‐catalyzed annulation of cyclic N‐sulfimines with γ‐ and δ‐hydroxy‐α,β‐unsaturated carbonyl compounds has proven to be a reliable method for the synthesis of oxazolines and 1,3‐oxazinanes. A mild and facile synthetic method for imidazolidine and oxazoline derivatives via the [3 + 2]‐annulation of cyclic N‐sulfimines has been established. The reactions between cyclic N‐sulfimines and γ‐sulfonamido/γ‐hydroxy‐α,β‐unsaturated ketones afforded a wide range of imidazolidine and oxazoline derivatives with excellent diastereoselectivities in the presence of Cs2CO3 or Et3N as a catalyst. In addition, the synthetic methodologies for the construction of hexahydropyrimidines and 1,3‐oxazinanes have been established through the [4 + 2] annulation between cyclic N‐sulfimines and δ‐sulfonamido/δ‐hydroxy‐α,β‐unsaturated ketones.