1: 78 percent / TMSOTf / CH2Cl2 / 0.5 h / -30 °C 2: 1.) H2, 2.) NaOMe / 1.) Pd/C / 1.) EtOH, HOAc, overnight, 2.) MeOH, room temperature, overnight View Scheme

boron trifluoride diethyl etherate in dichloromethane T=20°C; 0.75 h;

1: With trimethylsilylazide in 1,2-dichloro-ethane T=20°C; 0.166667 h; Molecular sieve; 2: With copper(II) bis(trifluoromethanesulfonate) in 1,2-dichloro-ethane T=60°C; 0.0333333 h; Microwave irradiation;

boron trifluoride diethyl etherate in dichloromethane T=-78°C; 1 h; Molecular sieve;