1: trimethylsilylacetylene With methylmagnesium bromide; zinc dibromide in tetrahydrofuran T=0°C; 0.5 h; 2: 1-bromo-2-iodoethylene With tetrakis(triphenylphosphine) palladium(0) in tetrahydrofuran T=20°C; 3 h; Further stages.;

(Z)-1,2-dibromoethylene; tetrakis(triphenylphosphine) palladium(0) in tetrahydrofuran 16 h; Ambient temperature;

1: 60 percent / MCPBA / CH2Cl2 / 16 h / 20 °C 2: 64 percent / CuBr; NH4Br; AcOH / tetrahydrofuran / 15 h / 70 °C 3: BF3*Et2O / CH2Cl2 / 0.33 h / 0 °C View Scheme

Yield given. Multistep reaction. Yields of byproduct given;