1: With hydrogen bromide; acetic acid; 4-hydroxy-benzoic acid T=20°C; 48 h; Inert atmosphere; 2: With water 2 h;

1.1: sodium hydride / N,N-dimethyl-formamide / 0.25 h / 0 °C 1.2: 4 h / 120 °C 2.1: hydrogenchloride; water / 24 h / 100 °C 3.1: triethylamine; diphenylphosphoranyl azide / toluene / 2 h / 90 °C 3.2: 2 h / Reflux 4.1: N-ethyl-N,N-diisopropylamine / 20 h / 125 °C / Inert atmosphere 5.1: 4-hydroxy-benzoic acid; hydrogen bromide; acetic acid / 48 h / 20 °C / Inert atmosphere 5.2: 2 h View Scheme

1.1: hydrogenchloride; water / 24 h / 100 °C 2.1: triethylamine; diphenylphosphoranyl azide / toluene / 2 h / 90 °C 2.2: 2 h / Reflux 3.1: N-ethyl-N,N-diisopropylamine / 20 h / 125 °C / Inert atmosphere 4.1: 4-hydroxy-benzoic acid; hydrogen bromide; acetic acid / 48 h / 20 °C / Inert atmosphere 4.2: 2 h View Scheme

1.1: triethylamine; diphenylphosphoranyl azide / toluene / 2 h / 90 °C 1.2: 2 h / Reflux 2.1: N-ethyl-N,N-diisopropylamine / 20 h / 125 °C / Inert atmosphere 3.1: 4-hydroxy-benzoic acid; hydrogen bromide; acetic acid / 48 h / 20 °C / Inert atmosphere 3.2: 2 h View Scheme

1.1: N-ethyl-N,N-diisopropylamine / 20 h / 125 °C / Inert atmosphere 2.1: 4-hydroxy-benzoic acid; hydrogen bromide; acetic acid / 48 h / 20 °C / Inert atmosphere 2.2: 2 h View Scheme