1: trimethylsilyl trifluoromethanesulfonate; propynoic acid ethyl ester With copper(l) iodide; lithium chloride in tetrahydrofuran T=-78°C; 0.0833333 h; Inert atmosphere; 2: methylmagnesium bromide in tetrahydrofuran T=-78°C; Inert atmosphere;

N,N,N',N',N'',N''-hexamethylphosphoric triamide; triethylamine T=-78°C; 8 h;