1: propynoic acid ethyl ester With n-butyllithium in tetrahydrofuran; hexane T=-78°C; 0.5 h; 2: methyloxirane With boron trifluoride diethyl etherate in tetrahydrofuran; hexane T=-78°C; 2 h;

1: triethyl orthopropiolate With n-butyllithium in tetrahydrofuran T=-78°C; 2: 4-methyl-[1,3,2]dioxathiolane 2,2-dioxide in tetrahydrofuran T=-78 - 20°C;

1: 100 percent 2: 1.) EtMgBr / 1.) THF, reflux, 1 h, 2.) -78 deg C, 1 h then 0 deg C, 2 h and 0-10 deg C, 2 h View Scheme

ethylmagnesium bromide 1.) THF, reflux, 1 h, 2.) -78 deg C, 1 h then 0 deg C, 2 h and 0-10 deg C, 2 h; Yield given. Multistep reaction;