1: 1.) aq. Na2S2O4, 2.) conc. H2SO4 / 2.) 20 -> 60 deg C 2: 70 percent / NaN(TMS)2 / tetrahydrofuran / 20 °C 3: 65 percent / NaHCO3 / Pd(OAc)2 / various solvent(s) / 15 h / 95 °C 4: 36 percent / CH2Cl2 / 4 h / Irradiation View Scheme

With  sodium dithionite; sulfuric acid  2.) 20 -> 60 deg C;  Yield given. Multistep reaction;   

Multi-step reaction with 2 steps 1: 1.) aq. Na2S2O4, 2.) conc. H2SO4 / 2.) 20 -> 60 deg C2: 70 percent / NaN(TMS)2 / tetrahydrofuran / 20 °C