in benzene 1) room temp., 15 min, 2) reflux, 1 h; Mechanism;

in benzene-d6 Ambient temperaturevarious reactant ratio; Product distribution;

1: With tert.-butyl lithium T=-78°C; 2: With selenium T=-78 - 20°C; 3: With ammonium chloride T=20°C;

in not given byproducts: I2; inert solvents; equilibrium mixt. monitored by UV and NMR;

tetraethylammonium iodide

sodium tetrahydroborate

1.1: Br2 / tetrahydrofuran; benzene / 0.75 h / 0 - 20 °C 2.1: n-BuLi / tetrahydrofuran; hexane / 0 °C 2.2: 87 percent / tetrahydrofuran; benzene; hexane / 2 h / 20 °C 3.1: DIBAL-H / hexane; toluene / 4 h / 0 - 20 °C 3.2: 92 percent / I2 / tetrahydrofuran; hexane; toluene / -78 - 20 °C 4.1: n-BuLi / tetrahydrofuran; hexane / 0.25 h / -78 °C 4.2: 100 percent / BF3*OEt2 / tetrahydrofuran; hexane / 1 h / -78 °C View Scheme