bromine; sodium acetate in chloroform T=0 - 20°C; 96 h;

potassium carbonate in acetone T=25°C; 1.5 h;

1: 99 percent / N-bromosuccinimide / dimethylformamide / 1 h / 25 °C 2: 79 percent / K2CO3 / acetone / 1.5 h / 25 °C View Scheme

1.1: hydrazine / dioxane 1.2: toluene / Heating 2.1: 99 percent / N-bromosuccinimide / dimethylformamide / 1 h / 25 °C 3.1: 79 percent / K2CO3 / acetone / 1.5 h / 25 °C View Scheme

1: 4-bromo-3-trifluoromethyl-1,5-dimethylpyrazole With tert.-butyl lithium in tetrahydrofuran; pentane T=-78°C; 0.05 h; 2: N,N-dimethyl-formamide in tetrahydrofuran; pentane T=-78 - 0°C; 2 h; 3: With hydrogenchloride; water in tetrahydrofuran; pentane T=20°C; 1 h;