1: 79 percent / p-toluenesulfonic acid / benzene / 1.5 h / 60 °C 2: 92 percent / diethyl ether / 0.08 h / 0 °C 3: 82 percent / pyridinium dichromate / CH2Cl2 / 6 h / Ambient temperature 4: 33 percent / LiCl, DMPU / 2.3 h / 170 °C View Scheme