Multi-step reaction with 5 steps 1: 80 percent / PCl3 / CHCl3 / 2 h / Heating2: 52 percent / NiCl2*6H2O/(C6H5)3P, Zn, KI / dimethylformamide / 12 h / 50 °C3: 53 percent / 30percent H2O2, (CH3CO)2O, / 14 h / 100 °C4: 77 percent / 33percent HBr/CH3COOH / 5 h / Heating5: 16 percent / methanol; diethyl ether