1: 98 percent / pyridine / CHCl3 2: 67 percent / n-butyl lithium, tetramethylethylenediamine / tetrahydrofuran 3: 88 percent / boron trichloride 4: 27 percent / Zn/Hg, 6N HCl / toluene / 2 h / Heating 5: 66 percent / oxygen, salcomine / dimethylformamide View Scheme