sodium hydroxide; hydrogen bromide; acetic anhydride; acetic acid; triethylamine; cobalt in ethanol; ethyl acetate; acetone

1.1: 2,6-dimethylpyridine / chloroform / 5 h / Inert atmosphere; Reflux 2.1: trifluoroacetic acid / dichloromethane / 1 h / 20 °C / Inert atmosphere; Cooling with ice 2.2: 55 °C / Inert atmosphere View Scheme