potassium carbonate in acetonitrile T=20°C;

boron trifluoride diethyl etherate in ethanol

boron trifluoride diethyl etherate 8 h; Heating;

1: COCl2 / toluene 2: triethylamine 3: 90 percent / boron trifluoride etherate / ethanol View Scheme

1: 1.) NaH; 2.) NBu4Br / 1.) toluene, reflux, 1 h; 2.) r.t., 24 h 2: 1.) 20 percent COCl2; 2.) triethylamine / 1.) chloroform, toluene, 5 h; 2.) r.t., 12 h 3: 90 percent / (Et)2O*BF3 / 8 h / Heating View Scheme