1: (diethoxy-phosphoryl)-fluoro-acetic acid ethyl ester With n-butyllithium in tetrahydrofuran; hexane T=0°C; 1 h; 2: butyraldehyde in tetrahydrofuran; hexane T=20°C;

lithium diisopropyl amide in tetrahydrofuran 2 h; Ambient temperature1.) -78 deg C, 1 h; 2.) room temp. 2 h; Yield given;