1: 94 percent / DBU / 7 h / 0 - 25 °C 2: 80 percent / BF3*Et2O / 0.5 h / -75 °C View Scheme

1: 94 percent / DBU / 7 h / 0 - 25 °C 2: 80 percent / BF3*Et2O / 0.5 h / -75 °C 3: toluene / 110 °C / sealed tube 4: p-TsOH*H2O / methanol / 16 h 5: 1.) (COCl)2, DMSO, 2.) Et3N / 1.) -40 deg C, 15 min. 6: 15 h / Ambient temperature 7: 97 percent / BF3*Et2O / nitromethane / 0.42 h / Ambient temperature View Scheme

Multi-step reaction with 2 steps 1: 94 percent / DBU / 7 h / 0 - 25 °C2: 80 percent / BF3*Et2O / 0.5 h / -75 °C  

Multi-step reaction with 5 steps 1: 94 percent / DBU / 7 h / 0 - 25 °C2: 80 percent / BF3*Et2O / 0.5 h / -75 °C3: toluene / 110 °C / sealed tube4: p-TsOH*H2O / methanol / 16 h5: 1.) (COCl)2, DMSO, 2.) Et3N / 1.) -40 deg C, 15 min.  

Multi-step reaction with 3 steps 1: 94 percent / DBU / 7 h / 0 - 25 °C2: 80 percent / BF3*Et2O / 0.5 h / -75 °C  

Multi-step reaction with 3 steps 1: 94 percent / DBU / 7 h / 0 - 25 °C2: 80 percent / BF3*Et2O / 0.5 h / -75 °C3: toluene / 110 °C / sealed tube  

Multi-step reaction with 4 steps 1: 94 percent / DBU / 7 h / 0 - 25 °C2: 80 percent / BF3*Et2O / 0.5 h / -75 °C3: toluene / 110 °C / sealed tube4: p-TsOH*H2O / methanol / 16 h  

Multi-step reaction with 6 steps 1: 94 percent / DBU / 7 h / 0 - 25 °C2: 80 percent / BF3*Et2O / 0.5 h / -75 °C3: toluene / 110 °C / sealed tube4: p-TsOH*H2O / methanol / 16 h5: 1.) (COCl)2, DMSO, 2.) Et3N / 1.) -40 deg C, 15 min.6: 15 h / Ambient temperature