1.1: 96 percent / p-toluenesulfonic acid monohydrate / benzene / 7 h / Heating 2.1: nBuLi / hexane; tetrahydrofuran / 1 h / -78 °C 2.2: 76 percent / hexane; tetrahydrofuran / 6 h / -78 °C 3.1: 98 percent / pyridinium tosylate; water / acetone / 16 h / Heating View Scheme

toluene-4-sulfonic acid in benzene 7 h; Heating;