sodium hydride in tetrahydrofuran 8 h; Heating;

1: (2-oxo-5-methyltetrahydrofuran-3-yl)-phosphonic acid diethyl ester With potassium carbonate in tetrahydrofuran; water T=20°C; 1 h; 2: cyclohexanecarbaldehyde in tetrahydrofuran; water T=70°C; 15 h;

sodium hydride in tetrahydrofuran 8 h; Heating;

1: 60 percent / Br2; PBr3 / 25 h / 100 °C 2: 84 percent / 5 h / 140 °C View Scheme

T=140°C; Arbuzov reaction; 5 h;

1.1: NaH / tetrahydrofuran / 0.67 h / 20 °C 1.2: tetrahydrofuran / 24 h / 20 °C 2.1: NaOMe / methanol / 0.5 h / 20 °C 2.2: H2SO4 / methanol / 2 h / -60 °C 3.1: NaBH4; aq. NaOH / methanol / 20 h / 20 °C View Scheme

1.1: piperidine / methanol / 0.5 h / Heating 1.2: 73 percent / methanol / 70 h / Heating 2.1: NaH / tetrahydrofuran / 0.67 h / 20 °C 2.2: 95 percent / tetrahydrofuran / 24 h / 20 °C 3.1: MeONa / methanol / 0.5 h / 20 °C 3.2: 95 percent / H2SO4 / methanol / 2 h / -60 °C 4.1: NaBH4; aq. NaOH / methanol / 20 h / 20 °C 5.1: aq. HCl View Scheme

potassium carbonate T=0 - 4°C; 0.25 h;