dipotassium peroxodisulfate; sodium hydroxide in water T=4°C; Inert atmosphere;

sodium dithionite in chloroform; water Ambient temperature;

1: 14.5 g / concentrated sulphuric acid / methanol / 1.) overnight at room temperature; 2.) reflux 6 h 2: 2.) sodium / 1.) water, ice cooling then to rt during 2 h; 2.) methanol, reflux, 1.25 h View Scheme