1: 72 percent / Et3N / CH2Cl2 / Heating 2: Et3N / methanol / 24 h / 20 °C View Scheme

1: in dichloromethane T=-78°C; Inert atmosphere; 2: With methanol in dichloromethane T=-78 - 20°C; 1 h; Inert atmosphere; 3: With methanol; sodium hydroxide in dichloromethane T=20°C; 1.5 h; Inert atmosphere;

bromine; tetra-n-butylammonium acetate in dichloromethane T=-78 - 20°C;