Formal [3 + 3] Annulation of Isatin-Derived 2-Bromoenals with 1,3-Dicarbonyl Compounds Enabled by Lewis Acid/N-Heterocyclic Carbene Cooperative Catalysis.

A series of novel isatin-derived 2-bromoenals were synthesized and applied in a formal [3 + 3] annulation with 1,3-dicarbonyl compounds enabled by a NHC/Lewis acid cooperative catalysis strategy. This newly developed methodology offers rapid access to functionalized spirooxindole δ-lactones. The newly synthesized isatin-derived 2-bromoenals may be further used as potential electrophilic 1,3-synthons for the diversity-oriented synthesis of spirooxindoles.