1: 1.) BF3-Et2O, 2.) bromine 2: 10 percent / 2,3-dichloro-5,6-dicyanobenzoquinone / toluene / 6 h / Heating View Scheme

1: 1.) BF3-Et2O, 2.) bromine 2: 46 percent / 2,3-dichloro-5,6-dicyanobenzoquinone / toluene / 6 h / Heating View Scheme

1: 1.) lithium di-isopropylamide, triethanolamine borate / 1.) THF, hexane, DMSO, -78 deg C, 2.) -20 deg C -> room temperature, 2 h 2: 1.) BF3-Et2O, 2.) bromine 3: 70 percent / selenium dioxide / dioxane / 96 h / Heating View Scheme

1: 1) N-bromosuccinimide, 2) water / 1) CCl4, reflux, 20 min, 2) THF, r.t., 1 h 2: 67 percent / pyridine, CrO3 / CH2Cl2 / 0.5 h / Ambient temperature 3: 90 percent / selenium dioxide / CH2Cl2; various solvent(s) / 2 h / Heating View Scheme