1: 87 percent / NaH / tetrahydrofuran / 2 h / 20 °C 2: 95 percent / NBS / CCl4 / 1.5 h / Heating 3: 80 percent / CuBr / pyridine / 14 h / Ambient temperature; addition at -30 deg C 4: TsOH / toluene / 20 h 5: H2O, 0.5n HCl / ethanol / Ambient temperature 6: alkali View Scheme

1: methanephosphonic acid dimethyl ester With n-butyllithium in tetrahydrofuran; hexane T=-78°C; 0.5 h; 2: hexane-1-carboxylic acid methyl ester in tetrahydrofuran; hexane T=-78°C; 2.16667 h;

n-butyllithium in tetrahydrofuran; hexane

1: 87 percent / NaH / tetrahydrofuran / 2 h / 20 °C 2: 95 percent / NBS / CCl4 / 1.5 h / Heating 3: 80 percent / CuBr / pyridine / 14 h / Ambient temperature; addition at -30 deg C 4: TsOH / toluene / 20 h 5: H2O, 0.5n HCl / ethanol / Ambient temperature View Scheme