Interaction of 1,3λ4δ2,2,4-benzodithiadiazines with neutral and charged S-electrophiles: SCl2, C6F5SCl, and NS2+

Reactions of 1,3λ4δ2,2,4-benzothiadiazines with SCl2, C6F5SCl, and [NS2][SbF6] leading to 1,2,3-benzodithiazolium salts (Herz salts) were investigated. The relative rate of reaction with SCl2 significantly depends on the nature of the substituent and its position in the carbocycle. Halogen substituents Cl, Br, and I slow down the reaction, especially if located closely to the heterocycle (positions 5 and 8). In the case of C6F5SCl and R = H, chlorination of the carbocycle and opening of the heterocycle also takes place with the formation of 7-chloro-1,3λ4δ2,2,4-benzothiadiazine and C6F5–S–N=S=N–Ar (Ar = 2-Cl-6-F5C6SC6H3), respectively. In the reaction with NS2+, along with contraction of the heterocycle, also its expansion occurs with the formation of 1,2,4λ4δ2,3,5-benzotrithiadiazepine.