1: 16 percent / DMAP; Et3N / 1,2-dichloro-ethane / 0.5 h / 75 °C 2: 97 percent / TFA; H2O / 2 h / 0 °C View Scheme

trifluoroacetic acid in acetonitrile T=0 - 20°C; 17 h;

1.1: 71 percent / DMAP; Et3N / 1,2-dichloro-ethane / 0.5 h / 75 °C 2.1: n-BuLi / tetrahydrofuran / -78 °C 2.2: 76 percent / tetrahydrofuran / 1 h / -78 °C 3.1: 96 percent / TFA; H2O / 12 h / 20 °C 4.1: 65 percent / Na2CO3; H2O / ethanol / 2 h / 100 °C View Scheme