1: 6-Fluoro-1H-indole With n-butyllithium; potassium tert-butylate in tetrahydrofuran; hexane T=-75°C; 2 h; 2: carbon dioxide in tetrahydrofuran; hexane cooling;

1.1: pyrrolidine / dimethylformamide / 6 h / Heating 1.2: 33 percent / Zn / acetic acid; H2O / 5 h / 100 °C 2.1: potassium tert-butoxide; BuLi / hexane; tetrahydrofuran / 2 h / -75 °C 2.2: 60 percent / hexane; tetrahydrofuran / cooling View Scheme