boron tribromide in dichloromethane T=-78 - 20°C; 14 h;

trifluorormethanesulfonic acid T=0 - 70°C; 29 h;

trifluorormethanesulfonic acid T=0 - 70°C; 28 h;

1: triethylamine / N,N-dimethyl-formamide / 1 h / 0 - 25 °C 2: trifluorormethanesulfonic acid / 29 h / 0 - 70 °C View Scheme

1.1: hydroxylamine hydrochloride; triethylamine / methanol / 2 h / 20 °C 2.1: 4-(N,N-dimethlyamino)pyridine; triethylamine / dichloromethane / 20 °C 3.1: methanesulfonyl chloride; boron trifluoride; titanium tetrachloride; methanol / 1,2-dichloro-ethane; methanol / 5 h / 20 °C 3.2: pH 7 4.1: boron tribromide / dichloromethane / 20 °C / Cooling with ice View Scheme

potassium carbonate in acetone 16 h; Heating;

potassium carbonate in acetone Reflux;