jones reagent in acetone T=20°C;

1: 9,9-dimethyl-9H-xanthene With n-butyllithium in tetrahydrofuran T=-78 - 20°C; 2: carbon dioxide T=-78 - 20°C;

1.1: n-butyllithium / tetrahydrofuran; hexane / 0.25 h / 20 °C 1.2: 73 percent / tetrahydrofuran; hexane / 0 - 1 °C 2.1: 95 percent / Jones reagent / acetone / 20 °C View Scheme