boron trichloride in dichloromethane T=-10°C; 0.5 h;

With  sodium chlorite; recorcinol in  1,4-dioxane 24 h;  pH 4.4;   

Multi-step reaction with 5 steps 1: 73 percent / copper bronze powder / 24 h / 200 - 210 °C2: 40 percent / hydrobromic acid, hydroiodic acid / 144 h / Heating3: 61 percent / potassium carbonate / acetone / 6 h4: 49 percent / titanium(IV) chloride / CH2Cl2 / 1 h / -10 °C5: 96 percent / sodium chlorite, resorcinol / dioxane / 24 h / pH 4.4  

Multi-step reaction with 4 steps 1: 40 percent / hydrobromic acid, hydroiodic acid / 144 h / Heating2: 61 percent / potassium carbonate / acetone / 6 h3: 49 percent / titanium(IV) chloride / CH2Cl2 / 1 h / -10 °C4: 96 percent / sodium chlorite, resorcinol / dioxane / 24 h / pH 4.4  

Multi-step reaction with 3 steps 1: 61 percent / potassium carbonate / acetone / 6 h2: 49 percent / titanium(IV) chloride / CH2Cl2 / 1 h / -10 °C3: 96 percent / sodium chlorite, resorcinol / dioxane / 24 h / pH 4.4  

Multi-step reaction with 2 steps 1: 49 percent / titanium(IV) chloride / CH2Cl2 / 1 h / -10 °C2: 96 percent / sodium chlorite, resorcinol / dioxane / 24 h / pH 4.4