1: Methyltriphenylphosphonium bromide With sodium hexamethyldisilazane in tetrahydrofuran T=-78°C; 0.5 h; 2: (S)-3-formylpyrrolidine-1-carboxylic acid t-butyl ester in tetrahydrofuran T=-78 - 20°C; 5 h;

1: With sodium iodide in ethylene glycol dimethyl ether T=50 - 60°C; 4 h; 2: With potassium tert-butylate in ethylene glycol dimethyl ether T=-10 - 20°C; Product distribution / selectivity;

1.1: potassium tert-butylate / 1-methyl-pyrrolidin-2-one / 35 - 40 °C 1.2: 18 h / 65 °C 1.3: pH 3 - 4 2.1: diethyl malonate; potassium hydroxide / water; tetrahydrofuran / 25 - 45 °C 2.2: 0.5 h / 5 - 10 °C 3.1: dimethyl sulfoxide / toluene / 2 h / Reflux 4.1: borane-THF / tetrahydrofuran / 2.75 h / 23 - 28 °C / Inert atmosphere 4.2: 1.67 h / 10 - 25 °C 5.1: triethylamine / toluene / -10 - 20 °C 6.1: sodium iodide / ethylene glycol dimethyl ether / 4 h / 50 - 60 °C 6.2: -10 - 20 °C View Scheme

1.1: borane-THF / tetrahydrofuran / 2.75 h / 23 - 28 °C / Inert atmosphere 1.2: 1.67 h / 10 - 25 °C 2.1: triethylamine / toluene / -10 - 20 °C 3.1: sodium iodide / ethylene glycol dimethyl ether / 4 h / 50 - 60 °C 3.2: -10 - 20 °C View Scheme

1.1: diethyl malonate; potassium hydroxide / water; tetrahydrofuran / 25 - 45 °C 1.2: 0.5 h / 5 - 10 °C 2.1: dimethyl sulfoxide / toluene / 2 h / Reflux 3.1: borane-THF / tetrahydrofuran / 2.75 h / 23 - 28 °C / Inert atmosphere 3.2: 1.67 h / 10 - 25 °C 4.1: triethylamine / toluene / -10 - 20 °C 5.1: sodium iodide / ethylene glycol dimethyl ether / 4 h / 50 - 60 °C 5.2: -10 - 20 °C View Scheme

1.1: dimethyl sulfoxide / toluene / 2 h / Reflux 2.1: borane-THF / tetrahydrofuran / 2.75 h / 23 - 28 °C / Inert atmosphere 2.2: 1.67 h / 10 - 25 °C 3.1: triethylamine / toluene / -10 - 20 °C 4.1: sodium iodide / ethylene glycol dimethyl ether / 4 h / 50 - 60 °C 4.2: -10 - 20 °C View Scheme