1: 98 percent / N,N-diisopropylethylamine / CH2Cl2 / a) r.t., 40 h, b) 30 deg C, 24 h 2: 1.09 g / Br2, NaHCO3 / CCl4 / Ambient temperature 3: 21 percent / 1,8-diazabicyclo<5.4.0>undec-7-ene / tetrahydrofuran / 168 h / 4 °C 4: 73 percent / KOH, H2O / ethanol / 24 h / Ambient temperature 5: 1) sec-BuLi, 2) Ac2O / 1) THF, hexane, -78 deg C, 2 h, 2) THF, -78 deg C, 2 h View Scheme

phosphorus tribromide in diethyl ether T=0°C;

1: 48percent HBr, conc. H2SO4 / 25 °C 2: 85 percent Spectr. / NaOC2H5 / ethanol / 3 h View Scheme

1: 48percent HBr, conc. H2SO4 / 25 °C 2: 15 percent Spectr. / NaOC2H5 / ethanol / 3 h View Scheme