1: pyridine 2: LiBr, LiCO3 / dimethylformamide / 75 °C 3: dimethylformamide / 75 °C 4: 86 percent / n-butyllithium / tetrahydrofuran / -20 °C 5: 5percent Na-Hg, Na2HPO4 / methanol / Ambient temperature 6: PPTS / ethanol 7: 1) irradiation, 2) thermal isomerization View Scheme

1: oxalyl chloride, triethylamine / dimethylsulfoxide 2: 1) lithium diisopropylamide / 1) THF, -78 deg C 3: 52 percent / 5percent Na-Hg, Na2HPO4 / 0 °C 4: 95 percent / 95percent ethanol / pyridinium p-toluenesulphonate / 40 °C 5: irradiation followed by thermal isomerization View Scheme