1: 1.) aq. HNO2, aq. HCl, 2.) SO2, HOAc, CuCl2*2H2O / 1.) 0 deg C, 20 min, 2.) water, from 0 deg C to RT, 1 h 2: H2O / 1.5 h / Heating View Scheme

in water 1.5 h; Heating; Yield given;