1: t-BuLi / tetrahydrofuran; pentane / 3.5 h / -78 - 0 °C 2: tetrahydrofuran; pentane / 1.5 h / -78 °C 3: SiO2 / benzene / 10 h / Heating View Scheme

1: ethyl α,α-dibromocaproate With tert.-butyl lithium in tetrahydrofuran; pentane T=-78 - 0°C; 3.5 h; 2: ethyl 5-oxo-5-phenylpentanoate in tetrahydrofuran; pentane T=-78°C; 5 h; 3: With silica gel in benzene 10 h; Heating; Further stages.;

1: t-BuLi / tetrahydrofuran; pentane / 3.5 h / -78 - 0 °C 2: 41 percent / tetrahydrofuran / -78 °C 3: silica gel / benzene / Heating View Scheme