1: n-butyllithium, LiBr / tetrahydrofuran / 0.75 h / 0 °C 2: 2.) phenyllithium, 3.) t-BuOK 3: 96 percent / CH3COOH, H2O / tetrahydrofuran / 1 h / Ambient temperature 4: 80 percent / pyridine / 48 h / Ambient temperature 5: 97 percent / NaH, 18-crown-6 / tetrahydrofuran / 3 h 6: 1.) n-butyllithium / 1.) THF, hexane, -23 deg C, 80 min, 2.) THF, hexane, 5 min 7: 1.) KH, 2.) tetrabutylammonium chloride, 18-crown-6 / 1.) THF, 15 min, 2.) THF, RT, 20 min 8: 86 percent / sodium naphthalenide / 1,2-dimethoxy-ethane / 0.67 h / -78 °C 9: 99 percent / K2CO3 / tetrahydrofuran; toluene 10: 85 percent / MeI, H2O / acetonitrile / Ambient temperature 11: 1.) t-BuLi, 2.) dineopentylzinc 12: (CH3)2SO, pyridine, CF3COOH, dicyclohexylcarbodiimide (DCC) / benzene / 0.5 h / Ambient temperature 13: benzene; diethyl ether / 0.33 h 14: n-Bu4NF / tetrahydrofuran / 0.25 h / 0 °C 15: 75percent aq. CH3COOH / tetrahydrofuran / 0 - 5 °C 16: 68 percent / diethyl cyanophosphonate, Et3N / dimethylformamide / 0.5 h / 0 °C 17: 86 percent / (COCl)2, (CH3)2SO / CH2Cl2 / 0.33 h / -78 °C 18: 69 percent / lithium bis(trimethylsilyl)amide / tetrahydrofuran / 2.5 h / 0 °C 19: 100 percent / 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), H2O / CH2Cl2 / 0.5 h / Ambient temperature 20: 64 percent / CF3COOH / 2.5 h / Ambient temperature View Scheme