Hydrochlorination and Hydrobromination of N-(N-Arylsulfonylbenzimidoyl)-1,4-benzoquinonimines

The direction of hydrohalogenation of N-substituted p-quinonimines was predicted on the basis of orbital coefficients of the C2 and C3 atoms in the lowest unoccupied molecular orbital, calculated by the PM3 method. It was assumed that the reaction is orbital-controlled and that the initial act of hydrohalogenation is nucleophilic attack by halide ion. The proposed approach was verified by experimental hydrochlorination and hydrobromination of N-(N-arylsulfonylbenzimidoyl)-1,4-benzoquinonimines which take up HHlg molecule following the 1,4-addition scheme, i.e., the halogen atom adds to C2 of the quinoid ring.