The sulfonylation reaction of aminonitriles 52 is carried out by the action of sulfonyl chlorides in the presence of an organic or inorganic base for deprotonation (Table ). For example, the common method described by Marco-Contelles and co-workers involves the sulfonylation of aminonitriles 52 with mesyl chloride (MsCl) or benzylsulfonyl chloride (BnSO2Cl) in the presence of triethylamine (Et3N) as a base in dichloromethane (CH2Cl2). For the further construction of the γ-sultam system, cyano sulfonamides 55 were subjected to N-alkylation using BnBr or isomeric chlorobenzyl derivatives (p-or m-ClC6H4CH2Cl) in the presence of K2CO3. This process led to the formation of tertiary cyano sulfonamides 56, which are then involved in the carbanyonic cyclization to give 4-amino-2,3-dihydroisothiazol-1,1-diones 57 in the presence of 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU), NaH or Cs2CO3. The literature sources highlighted that attempts to synthesize βenaminosaltums 57 with an unsubstituted nitrogen atom in the 1-position of the heterocyclic fragment from secondary sulfonamides 56 were unsuccessful due to the presence of an acidic NH proton of the secondary sulfonamide group. Mesylation of cyclic aminonitriles 53a-c led to the formation of sulfonamides 58a-c, which were subjected to carbanion cyclization for the synthesis of spirocyclic β-enamino-γ-sultams 59a-c using t-BuOK as a base in DMF (Table ). Notably, β-enamino-γ-saltams 59a-c could be readily transformed into the corresponding β-keto-γ-saltams 60a-c in up to 95% yield. 87 Moreover, this approach allows for the introduction of other alkyl groups near the sultam nitrogen atom. For instance, N-ethyl-substituted spirocyclic sultam 61 was synthesized from 1-aminocyclohexanecarbonitrile 62 via sulfonylation (43% yield). Sulfonamide 63 thus obtained was subjected to alkylation with ethyl iodide to give sulfonamide 64. This compound serves as a precursor for cyclization to the corresponding sultam 61 upon the action of t-BuOK in DMF (Scheme 7). 88 The synthetic sequence involving mesylation and carbanionic cyclization is particularly interesting for sterically hindered α-aminonitriles. Steric factor was achieved by incorporating an additional methyl group into the carbocyclic substituent or by attaching ethyl or isopropyl group to the nitrogen atom of aminonitrile. Mesylation of α-(N-ethylamino)-and α-(N-propylamino)-α,α-disubstituted aminonitriles 65a-c, as well as their isomeric α-N-methyl-substituted derivatives with an additional methyl substituent in all positions of cyclopentane and cyclohexane cores of 65d-i, resulted in the formation of alternative products of the CSIC reaction, namely β-amino-α-mesyl-γsultams 66a-i in 16-44% yield (Table ). The proposed mechanism for the formation of β-amino-α-mesyl-γ-sultams 66 from sterically hindered aminonitriles 65 involves the base-catalyzed initial dimerization of mesyl chloride, leading to the formation of reactive mesylsulfene 67.