1: LiBr, LiCO3 / dimethylformamide / 75 °C 2: dimethylformamide / 75 °C 3: 86 percent / n-butyllithium / tetrahydrofuran / -20 °C 4: 5percent Na-Hg, Na2HPO4 / methanol / Ambient temperature 5: PPTS / ethanol 6: 1) irradiation, 2) thermal isomerization View Scheme