1: methyllithium With copper (I) cyanide in tetrahydrofuran; hexane T=-78 - 20°C; 0.166667 h; Inert atmosphere; 2: (E)-1-(tert-butyldimethylsilyl)-2,3-dibromobut-2-en-1-one in tetrahydrofuran; hexane T=-78°C; 3 h; Inert atmosphere;