1: 95 percent / oxalyl chloride / benzene / 50 °C 2: 98 percent / pyridine / CHCl3 3: 67 percent / n-butyl lithium, tetramethylethylenediamine / tetrahydrofuran 4: 88 percent / boron trichloride 5: 27 percent / Zn/Hg, 6N HCl / toluene / 2 h / Heating 6: 66 percent / oxygen, salcomine / dimethylformamide View Scheme