1: 2-diphenylphosphinoyl-4-methyl-pentan-3-one With sodium methylate in tetrahydrofuran T=20°C; 0.25 h; 2: 1-[(E)-3-bromo-1-propenyl]benzene in tetrahydrofuran T=20°C; 24 h; Further stages.;

1.1: n-BuLi / tetrahydrofuran / 0.25 h / 0 °C 1.2: 65 percent / tetrahydrofuran / 2.5 h / -78 °C 2.1: NaOMe / tetrahydrofuran / 0.25 h / 20 °C 2.2: 80 percent / tetrahydrofuran / 24 h / 20 °C View Scheme