The general procedure for the synthesis of isoquinoline-5-sulfonyl chloride from 5-isoquinolinesulfonic acid was as follows: 5-isoquinolinesulfonic acid was placed in a round-bottomed flask, 6 mL of thionyl chloride and 1 drop of N,N-dimethylformamide (DMF) were added, and the reaction was carried out at reflux for 3 hours. Upon completion of the reaction, the excess thionyl chloride was removed using a rotary evaporator. Dichloromethane (DCM) was added to the residual solid and the solid product was collected by filtration. The solid was washed three times with DCM and subsequently dried in a vacuum oven to give a white solid intermediate 2 (1 g, 91.9% yield). Intermediate 2 (130.00 mg, 571.01 μmol) was slowly added to a solution of DCM (6 mL) containing ethylenediamine (381.30 μL, 5.71 mmol) under ice-bath conditions. After removing the ice bath, the mixture was allowed to react for 3 h at room temperature. Upon completion of the reaction, the mixture was washed with water to remove the remaining ethylenediamine. The organic phase was removed using a rotary evaporator and the residue was recrystallized by ether to give brown solid 3 (91.8 mg, 60% yield).
