triethylamine in tetrahydrofuran 1.) 0 deg C, 15 min, 2.) r.t., 15 min;

1: 71 percent / CH2Cl2 / Ambient temperature 2: 65 percent / mesyl chloride, NEt3 / tetrahydrofuran / 0.33 h 3: 95 percent / NEt3 / tetrahydrofuran / 1.) 0 deg C, 15 min, 2.) r.t., 15 min View Scheme