1: Methyltriphenylphosphonium bromide With n-butyllithium in tetrahydrofuran T=-78 - 20°C; 2: 3-formyl-4-vinyl-cyclopentene-1,1-dicarboxylic acid diethyl ester in tetrahydrofuran T=-78°C; 2 h;

1.1: RuCp(NCMe)3PF6 / acetone; H2O / 1.5 h / 60 °C 2.1: n-BuLi / tetrahydrofuran / -78 - 20 °C 2.2: 14 percent / tetrahydrofuran / 2 h / -78 °C View Scheme

1.1: NaH / dimethylformamide; various solvent(s) 1.2: NaI / dimethylformamide; various solvent(s) / 40 h 1.3: 53 percent / aq. HCl / dimethylformamide / 4 h 2.1: RuCp(NCMe)3PF6 / acetone; H2O / 1.5 h / 60 °C 3.1: n-BuLi / tetrahydrofuran / -78 - 20 °C 3.2: 14 percent / tetrahydrofuran / 2 h / -78 °C View Scheme

1.1: NaOEt / ethanol; various solvent(s) / 1 h 1.2: 47 percent / ethanol; toluene; various solvent(s) / 21 h / 0 - 20 °C 2.1: NaH / dimethylformamide; various solvent(s) 2.2: NaI / dimethylformamide; various solvent(s) / 40 h 2.3: 53 percent / aq. HCl / dimethylformamide / 4 h 3.1: RuCp(NCMe)3PF6 / acetone; H2O / 1.5 h / 60 °C 4.1: n-BuLi / tetrahydrofuran / -78 - 20 °C 4.2: 14 percent / tetrahydrofuran / 2 h / -78 °C View Scheme