1: 80 percent / disodium dithionite / aq. ethanol / 2 h / Heating 2: 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide / toluene / 15 h / Heating 3: 80 percent / anhydrous hydrazine / ethanol / 4 h / Heating View Scheme

sodium dithionite in ethanol 2 h; Heating;