1: With trifluoroacetic anhydride in benzene T=20°C; Pummerer reaction; 0.5 h; 2: With boron trifluoride diethyl etherate in benzene T=20°C; Pummerer reaction; 24 h;

1.1: oxalyl chloride / 2 h / 20 °C 2.1: 97 percent / Et3N / benzene / 17 h / 20 °C 3.1: 100 percent / KOH; tetrabutylammonium bromide / tetrahydrofuran / 5.5 h / 20 °C 4.1: 99 percent / aq. NaIO4 / methanol / 6 h / 20 °C 5.1: TFAA / benzene / 0.5 h / 20 °C 5.2: 43 percent / BF3*Et2O / benzene / 24 h / 20 °C View Scheme

1.1: 97 percent / Et3N / benzene / 17 h / 20 °C 2.1: 100 percent / KOH; tetrabutylammonium bromide / tetrahydrofuran / 5.5 h / 20 °C 3.1: 99 percent / aq. NaIO4 / methanol / 6 h / 20 °C 4.1: TFAA / benzene / 0.5 h / 20 °C 4.2: 43 percent / BF3*Et2O / benzene / 24 h / 20 °C View Scheme

1.1: 91 percent / KOH / ethanol / 2 h / Heating 2.1: oxalyl chloride / 2 h / 20 °C 3.1: 97 percent / Et3N / benzene / 17 h / 20 °C 4.1: 100 percent / KOH; tetrabutylammonium bromide / tetrahydrofuran / 5.5 h / 20 °C 5.1: 99 percent / aq. NaIO4 / methanol / 6 h / 20 °C 6.1: TFAA / benzene / 0.5 h / 20 °C 6.2: 43 percent / BF3*Et2O / benzene / 24 h / 20 °C View Scheme

1.1: 100 percent / KOH; tetrabutylammonium bromide / tetrahydrofuran / 5.5 h / 20 °C 2.1: 99 percent / aq. NaIO4 / methanol / 6 h / 20 °C 3.1: TFAA / benzene / 0.5 h / 20 °C 3.2: 43 percent / BF3*Et2O / benzene / 24 h / 20 °C View Scheme

1.1: 99 percent / aq. NaIO4 / methanol / 6 h / 20 °C 2.1: TFAA / benzene / 0.5 h / 20 °C 2.2: 43 percent / BF3*Et2O / benzene / 24 h / 20 °C View Scheme