1: LDA / tetrahydrofuran / 2 h / 0 °C / adding, -70 deg C 2: tetrahydrofuran / cooling, then 1 h, room t. 3: Et3N / tetrahydrofuran / 0 deg C, then 2 h, room t. 4: 51 percent / LDA(3 equiv.) / tetrahydrofuran / 23 h / Ambient temperature; addition, -70 deg C View Scheme

lithium diisopropyl amide in tetrahydrofuran T=0°C; 2 h; adding, -70 deg C;

1: LDA / tetrahydrofuran / 2 h / 0 °C / adding, -70 deg C 2: tetrahydrofuran / cooling, then 1 h, room t. 3: Et3N / tetrahydrofuran / 0 deg C, then 2 h, room t. 4: 78 percent / LDA / tetrahydrofuran / 4 h / 0 °C / adding, -70 deg C View Scheme

lithium diisopropyl amide in tetrahydrofuran T=0°C; 2 h; adding, -70 deg C;