trifluoroacetic acid in chloroform T=21°C; 72 h;

1: 60 percent / LDA, HMPA / tetrahydrofuran / 0.5 h / -78 °C 2: 99 percent / KHMDS / tetrahydrofuran / 1 h / -78 - 21 °C 3: 99 percent / diethyl ether / -78 - 21 °C 4: 80 percent / 35percent aq. CF3COOH / CHCl3 / 72 h / 21 °C View Scheme

1: 99 percent / KHMDS / tetrahydrofuran / 1 h / -78 - 21 °C 2: 99 percent / diethyl ether / -78 - 21 °C 3: 80 percent / 35percent aq. CF3COOH / CHCl3 / 72 h / 21 °C View Scheme

1: 99 percent / diethyl ether / -78 - 21 °C 2: 80 percent / 35percent aq. CF3COOH / CHCl3 / 72 h / 21 °C View Scheme