One of the prominent strategies for constructing fused sultams, particularly five-membered derivatives, involves the 1,3-dipolar [3+2] cycloaddition reactions. This transformation relies on the use of partially unsaturated sultams featuring an imine bond C=N, which acts as a 2πelectron component (Scheme 2). For instance, the imine derivative of saccharin 33 undergoes a palladium-catalyzed enantioselective annulation reaction with nitrile-substituted allylsilane 34, serving as a precursor of trimethylene methane (2π-electron component). This results in the formation of a pyrrolidine ring 35. Compound 34 contains trimethylsilyl (TMS) and acetate (OAc) groups, which undergo cleavage upon the action of a palladium catalyst in the presence of ligand 36. Consequently, a three-center twoelectron bond forms with palladium, along with a carbanion stabilized by a nitrile group, which then nucleophilically attacks the imine carbon atom, leading to further cyclization into a tricyclic sultam with high enantio-and diastereoselectivity (85% yield). Another notable application of benzoisothiazole derivatives 37a-n involves enantioselective organocatalytic cycloaddition reactions with derivatives 38 to give azaspirooxyindole derivatives 39a-n, featuring a fused sultam fragment. The alkaloid organocatalyst 40, containing a tertiary amine moiety as the main functional group, interacts with substituted acrylates 38. Subsequent transformations involve the removal of O-Boc group and the formation of anions, which then attach to the imine carbon of sultams 37. The final step entails the replacement of the alkaloid moiety with the sulfonamide nitrogen atom, leading to cyclization and the formation of spirocyclic derivatives 39 (Table ). 67 Furthermore, another annulation reaction utilizes sulfoimine 41 and involves the use of vinylcyclopropane 42, wherein the strained cycle undergoes opening under the action of a palladium catalyst. Consequently, a carbanion stabilized by two nitrile groups is formed, which subsequently attaches to the imine, leading to cyclization and the formation of tricyclic sultam 43 (Scheme 3). 68 Scheme 3. Palladium-catalyzed 1,3-dipolar cycloadditionannealation of vinylcyclopropane 42 and unsaturated sultam 41 for the synthesis of 43