1: methylmagnesium bromide With copper(I) bromide dimethylsulfide complex in tetrahydrofuran T=-78°C; 0.5 h; Inert atmosphere; 2: 2-acetoxy-5,5-dimethyl-2-phenylethynyl-1,3-dioxane in tetrahydrofuran T=-78 - 20°C; Inert atmosphere; 3: With sulfuric acid in methanol T=0°C; 0.5 h; Inert atmosphere;

1.1: tetrahydrofuran / 1 h / 0 °C / |Inert atmosphere 1.2: 1 h / 0 °C / |Inert atmosphere 2.1: copper(I) bromide dimethylsulfide complex / tetrahydrofuran / 0.5 h / -78 °C / |Inert atmosphere 2.2: -78 - 20 °C / |Inert atmosphere 2.3: 0.5 h / 0 °C / |Inert atmosphere View Scheme