(i) O2, rose bengal, NaOAc, MeOH, (UV-irradiation), (ii) aq. HCl, THF; Multistep reaction;

1: 68 percent / pyridinium dichromate / dimethylformamide / 2 h / Ambient temperature 2: 1.) N-Bromosuccinimide, 2.) DABCO, 4-(dimethylamino)pyridine / 1.) CH2Cl2, CCl4, 50 deg C, 2.) 80 deg C, (25mm Hg) View Scheme

dipyridinium dichromate in N,N-dimethyl-formamide 2 h; Ambient temperature;