1: 1-chloro-3,6-dimethoxybenzocyclobutene With magnesium in tetrahydrofuran Heating; 2: carbon dioxide in tetrahydrofuran T=20°C; 0.5 h;

Multi-step reaction with 3 steps 1: 59 percent / silver(I) tetrafluoroborate / 3 h / 50 °C2: 74 percent / triethylamine, 4-dimethylaminopyridine / CH2Cl2 / 1.25 h / 0 °C3: 15 percent / CDCl3 / 1.) 100 deg C to 110 deg C, 10 d, 2.) 135 deg C to 140 deg C, 4 d  

Multi-step reaction with 2 steps 1: 78 percent / Amberlyst 15 ion exchange resin / methanol / Ambient temperature2: 80 percent / pyridine, thionyl chloride / diethyl ether / 1 h / Heating