titanium tetrachloride in hexane T=20°C; 24 h;

lithium in tetrahydrofuran T=-45°C; 16 h; further β-bromoenamine,; Product distribution;

titanium tetrachloride in hexane T=110°C; 4 h;

1: 1.) Br2; 2.) triethylamine / 1.) ether, -60 deg C, 0.5 h; 2.) ether, -20 to -30 deg C, 0.5 h 2: H2O / diethyl ether / 0.5 h / Ambient temperature View Scheme

1: 1.) Br2 2.) NEt3 / 1.) ether, -60 deg C, 0.5 h, then 0 deg C; 2.) ether, -20 deg C 2: 100 percent / n-butyllithium / tetrahydrofuran; diethyl ether / 0.25 h / -70 °C 3: tetrahydrofuran / 0.5 h / -65 °C 4: 1.2 N HCl / H2O / 0.5 h / Ambient temperature View Scheme

ozone in pyridine; dichloromethane T=-70°C; Yield given. Yields of byproduct given;

ammonium cerium(IV) nitrate in acetonitrile 0.5 h; Ambient temperature;