boron tribromide in dichloromethane T=25°C; 18 h;

1: 18 h / 110 °C 2: H2SO4, CF3COOH / 2 h / Heating 3: aq. HCOOH / 4.5 h / Heating 4: BBr3 / CH2Cl2 / 18 h / 25 °C View Scheme

1: aq. HCOOH / 4.5 h / Heating 2: BBr3 / CH2Cl2 / 18 h / 25 °C View Scheme

1: 18 h / 110 °C 2: H2SO4, CF3COOH / 2 h / Heating 3: aq. HCOOH / 4.5 h / Heating 4: BBr3 / CH2Cl2 / 18 h / 25 °C View Scheme

1: H2SO4, CF3COOH / 2 h / Heating 2: aq. HCOOH / 4.5 h / Heating 3: BBr3 / CH2Cl2 / 18 h / 25 °C View Scheme

1: 1.) 50percent NaH suspension in mineral oil, Me2SO / 1.) THF, 0 deg C, 5 min, 2.) a) 0 deg C, 15 min, b) 25 deg C, 2h 2: 18 h / 110 °C 3: H2SO4, CF3COOH / 2 h / Heating 4: aq. HCOOH / 4.5 h / Heating 5: BBr3 / CH2Cl2 / 18 h / 25 °C View Scheme