toluene-4-sulfonic acid in benzene 1 h; Heating;

1: HOBr 2: CrO3, H2SO4 / acetone 3: 58 percent / dimethylformamide / 4 h / 25 °C 4: 1.) LDA, 2.) pTsOH / 1.) THF, -70 deg C to 0 deg C, 0.5 h, 2.) CH2Cl2, 25 deg C, 1 h 5: 55 percent / Na-Hg, KH2PO4 / methanol / 25 °C View Scheme

1: 58 percent / dimethylformamide / 4 h / 25 °C 2: 1.) LDA, 2.) pTsOH / 1.) THF, -70 deg C to 0 deg C, 0.5 h, 2.) CH2Cl2, 25 deg C, 1 h 3: 55 percent / Na-Hg, KH2PO4 / methanol / 25 °C View Scheme

1: CrO3, H2SO4 / acetone 2: 58 percent / dimethylformamide / 4 h / 25 °C 3: 1.) LDA, 2.) pTsOH / 1.) THF, -70 deg C to 0 deg C, 0.5 h, 2.) CH2Cl2, 25 deg C, 1 h 4: 55 percent / Na-Hg, KH2PO4 / methanol / 25 °C View Scheme

1: 1.) n-BuLi / 1.) THF, -78 deg C, 1 h; 2.) -78 deg C, 1 h 2: 75 percent / tetrahydrofuran / 12 h / Ambient temperature 3: 83 percent / DIBAL / diethyl ether / 1.5 h / -30 °C 4: 75 percent / p-toluenesulfonic acid / benzene / 1 h / Heating View Scheme

1: 83 percent / DIBAL / diethyl ether / 1.5 h / -30 °C 2: 75 percent / p-toluenesulfonic acid / benzene / 1 h / Heating View Scheme

1: 75 percent / tetrahydrofuran / 12 h / Ambient temperature 2: 83 percent / DIBAL / diethyl ether / 1.5 h / -30 °C 3: 75 percent / p-toluenesulfonic acid / benzene / 1 h / Heating View Scheme