1: With thionyl chloride T=-60°C; 1 h; 2: With sodium hydrogencarbonate in water; ethyl acetate

1.1: chloroformic acid ethyl ester; triethylamine / tetrahydrofuran / 0 - 20 °C / Inert atmosphere 1.2: 0 - 20 °C 2.1: thionyl chloride / dichloromethane; N,N-dimethyl-formamide / 20 °C / Cooling with ice View Scheme

in N,N-dimethyl-formamide T=20°C; 48 h;