water; oxalic acid; silica gel in tetrachloromethane 16 h; Ambient temperature;

hydrogen cation in tetrachloromethane Ambient temperature;

4-methylpyridine 1-oxide; (IPr)AuCl; bis-(trifluoromethylsulphonyl)amine; AgNTf2 in dichloromethane T=20°C; 19 h;

lithium bromide in tetrachloromethane T=45°C; 1.25 h;

1.1: n-butyllithium / tetrahydrofuran; hexane / 0.5 h / -78 °C 1.2: 1 h / -78 °C 2.1: 4-methylpyridine 1-oxide; (IPr)AuCl; AgNTf2; bis-(trifluoromethylsulphonyl)amine / dichloromethane / 19 h / 20 °C View Scheme