tert.-butyl lithium in tetrahydrofuran; pentane -78 deg C to room temperature;

2,3,5-trimethyl-pyridine; PPh3.Br2 in dichloromethane T=0°C; 0.25 h;

1: pyridinium chlorochromate, sodium acetate / CH2Cl2 / 1.5 h 2: tetrahydrofuran; diethyl ether / -78 °C 3: 86 percent / pyridinium chlorochromate, sodium acetate / CH2Cl2 / 1.5 h 4: 52 percent / p-toluenesulfonic acid / 7 h / Heating 5: 1.) n-butyllithium / 1.) THF, hexane, -78 deg C 2.) THF, hexane, 0 deg C 6: 54 percent / P(C6H5)3*Br2, collidine / CH2Cl2 / 0.25 h / 0 °C View Scheme

1: 52 percent / p-toluenesulfonic acid / 7 h / Heating 2: 1.) n-butyllithium / 1.) THF, hexane, -78 deg C 2.) THF, hexane, 0 deg C 3: 54 percent / P(C6H5)3*Br2, collidine / CH2Cl2 / 0.25 h / 0 °C View Scheme

1: tetrahydrofuran; diethyl ether / -78 °C 2: 86 percent / pyridinium chlorochromate, sodium acetate / CH2Cl2 / 1.5 h 3: 52 percent / p-toluenesulfonic acid / 7 h / Heating 4: 1.) n-butyllithium / 1.) THF, hexane, -78 deg C 2.) THF, hexane, 0 deg C 5: 54 percent / P(C6H5)3*Br2, collidine / CH2Cl2 / 0.25 h / 0 °C View Scheme

1: 86 percent / pyridinium chlorochromate, sodium acetate / CH2Cl2 / 1.5 h 2: 52 percent / p-toluenesulfonic acid / 7 h / Heating 3: 1.) n-butyllithium / 1.) THF, hexane, -78 deg C 2.) THF, hexane, 0 deg C 4: 54 percent / P(C6H5)3*Br2, collidine / CH2Cl2 / 0.25 h / 0 °C View Scheme

1: 1.) n-butyllithium / 1.) THF, hexane, -78 deg C 2.) THF, hexane, 0 deg C 2: 54 percent / P(C6H5)3*Br2, collidine / CH2Cl2 / 0.25 h / 0 °C View Scheme

tert.-butyl lithium in tetrahydrofuran; pentane -78 deg C to room temperature;