methanesulfonyl chloride; triethylamine in dichloromethane T=0 - 40°C; 1.5 h;

1: LDA / tetrahydrofuran / 0.75 h / -78 - -30 °C 2: 87 percent / Ambient temperature 3: 97 percent / Et3N, MsCl / CH2Cl2 / 1.5 h / 0 - 40 °C View Scheme

toluene-4-sulfonic acid in xylene 4 h; Heating;