1: 1-benzyl-3-bromoindazole With isopropylmagnesium chloride in tetrahydrofuran T=-10°C; 7 h; Inert atmosphere; 2: formaldehyd in tetrahydrofuran T=0°C; 3: With phosphoric acid in tetrahydrofuran

1.1: isopropylmagnesium chloride / tetrahydrofuran / 7 h / -10 °C / Inert atmosphere 1.2: 0 °C 2.1: hydrogenchloride / toluene; water / 2 h / 90 °C 3.1: sodium hydride / N,N-dimethyl-formamide; toluene / 1.5 h / Inert atmosphere 3.2: 10 h / 90 °C 4.1: sodium hydroxide / 3 h / Reflux View Scheme