toluene-4-sulfonic acid in acetonitrile 0.5 h; Ambient temperatureabsence of light;

in diethyl ether 1 h; Heating;

1: 71 percent / n-butyl-lithium, di-isopropylamine / tetrahydrofuran / 1.) -78 deg C, 3.5 h, 2.) room temperature, 18 h 2: 83 percent / H2SO4 / 120 h / Heating 3: 89 percent / diethyl ether / 1 h / Heating View Scheme

1: 83 percent / H2SO4 / 120 h / Heating 2: 89 percent / diethyl ether / 1 h / Heating View Scheme

1: 96 percent / toluene-p-sulphonic acid monohydrate / acetonitrile / 0.5 h / Ambient temperature; absence of light 2: 93 percent / CCl4 / 12 h / Irradiation; sunlight View Scheme