1: 56 percent / conc. H2SO4, HNO3 / acetic acid / 2 h / Ambient temperature 2: 58 percent / tetrahydrofuran / 8 h / Heating 3: 93 percent / acetic acid / Ambient temperature 4: 71 percent / acetic acid, sodium triacetoxyborohydride / 1,2-dichloro-ethane View Scheme

1: 58 percent / tetrahydrofuran / 8 h / Heating 2: 93 percent / acetic acid / Ambient temperature 3: 71 percent / acetic acid, sodium triacetoxyborohydride / 1,2-dichloro-ethane View Scheme

1: 82.5 percent / potassium hydroxide / various solvent(s) / 4 h / 57 °C / solvent: N-methyl-pyrrolidinone 2: aq. HCl 3: 94 percent / thionyl chloride / 3 h / Heating 4: 1.) sodium hydrosulfite, 2.) aq. HCl / 1.) THF, ethanol, water, steam bath, 4 h, 2.) THF, ethanol, 15 min, steam bath View Scheme

1: 82.5 percent / potassium hydroxide / various solvent(s) / 4 h / 57 °C / solvent: N-methyl-pyrrolidinone 2: aq. HCl 3: 94 percent / thionyl chloride / 3 h / Heating 4: 1.) sodium hydrosulfite, 2.) aq. HCl / 1.) THF, ethanol, water, steam bath, 4 h, 2.) THF, ethanol, 15 min, steam bath View Scheme