1: 71 percent / 2-methyl-propan-2-ol / 96 h / 25 °C 2: 72.7 percent / DBU / methanol / 48 h / 25 °C 3: 70 percent / K2CO3 / dimethylformamide / 24 h / 25 °C View Scheme

in tert-butyl alcohol T=25°C; 96 h;