Hg(OTf)2; N,N,N',N'-tetramethyl-urea in acetonitrile T=20°C; 0.5 h;

1.1: LDA / tetrahydrofuran / 0.5 h / -78 °C 1.2: 77 percent / tetrahydrofuran / -78 - 20 °C 2.1: aqueous HCl / acetone / 8 h / 20 °C 3.1: 90 percent / W(CO)6 / tetrahydrofuran / 20 °C / UV-irradiation View Scheme

1.1: 93 percent / p-toluenesulfonic acid monohydrate / benzene / 12 h / Heating 2.1: LDA / tetrahydrofuran / 0.5 h / -78 °C 2.2: 77 percent / tetrahydrofuran / -78 - 20 °C 3.1: aqueous HCl / acetone / 8 h / 20 °C 4.1: 90 percent / W(CO)6 / tetrahydrofuran / 20 °C / UV-irradiation View Scheme