1-propanephosphonic acid cyclic anhydride; N-ethyl-N,N-diisopropylamine in dichloromethane; ethyl acetate T=-40°C; 0.5 h;

1.1: 1,4-diaza-bicyclo[2.2.2]octane / N,N-dimethyl-formamide / 0.5 h 1.2: 1 h 2.1: lithium hydroxide hydrate; water / tetrahydrofuran / 4 h / 20 °C 3.1: 1-propanephosphonic acid cyclic anhydride; N-ethyl-N,N-diisopropylamine / dichloromethane; ethyl acetate / 0.5 h / -40 °C View Scheme

1.1: NaHS monohydrate / N,N-dimethyl-formamide / 0.42 h / 10 °C / |Inert atmosphere; |Large scale 1.2: 0.83 h / 10 °C / |Large scale 2.1: hydrazine hydrate / N,N-dimethyl-formamide / 2 h / 10 °C / |Inert atmosphere; |Large scale 2.2: 13 h / 0 - 100 °C / |Large scale 3.1: 1,4-diaza-bicyclo[2.2.2]octane / N,N-dimethyl-formamide / 0.5 h 3.2: 1 h 4.1: lithium hydroxide hydrate; water / tetrahydrofuran / 4 h / 20 °C 5.1: 1-propanephosphonic acid cyclic anhydride; N-ethyl-N,N-diisopropylamine / dichloromethane; ethyl acetate / 0.5 h / -40 °C View Scheme

1.1: hydrazine hydrate / N,N-dimethyl-formamide / 2 h / 10 °C / |Inert atmosphere; |Large scale 1.2: 13 h / 0 - 100 °C / |Large scale 2.1: 1,4-diaza-bicyclo[2.2.2]octane / N,N-dimethyl-formamide / 0.5 h 2.2: 1 h 3.1: lithium hydroxide hydrate; water / tetrahydrofuran / 4 h / 20 °C 4.1: 1-propanephosphonic acid cyclic anhydride; N-ethyl-N,N-diisopropylamine / dichloromethane; ethyl acetate / 0.5 h / -40 °C View Scheme

1: lithium hydroxide hydrate; water / tetrahydrofuran / 4 h / 20 °C 2: 1-propanephosphonic acid cyclic anhydride; N-ethyl-N,N-diisopropylamine / dichloromethane; ethyl acetate / 0.5 h / -40 °C View Scheme