1: 75 percent / tetrahydrofuran / 15 h / Ambient temperature 2: 74 percent / POCl3 / CH2Cl2 / 20 h / Heating 3: 90 percent / NaBH3CN, HCl / ethanol; tetrahydrofuran / 20 h / Ambient temperature 4: 80 percent / Et3N / tetrahydrofuran / 72 h / Heating 5: 87 percent / 1N aq. KOH / ethanol / 18 h / Ambient temperature View Scheme

triethylamine in benzene 1 h; Ambient temperature;