thionyl chloride; N,N-dimethyl-formamide 4 h; Heating;

1: 1) Na; 2) SO2 / 1) THF, paraffin oil, r.t., overnight; 2) neat (solid phase), 4-6 h 2: 70 percent / CrO3, conc. H2SO4 / 2 h / 75 °C 3: 90 percent / SOCl2, DMF / 4 h / Heating View Scheme

1: 70 percent / CrO3, conc. H2SO4 / 2 h / 75 °C 2: 90 percent / SOCl2, DMF / 4 h / Heating View Scheme