1: dichloromethane / 3 h / 20 - 45 °C / Reflux 2: triethylamine; 4-toluenesulfonyl azide / dichloromethane / 2 h / 20 - 30 °C 3: hydrogenchloride; methanol / dichloromethane; water / 3 h / 20 - 30 °C 4: dichloromethane; isopropanol acetate / 25 - 30 °C 5: zinc dibromide; dirhodium(II) tetraoctanoate / dichloromethane / 40 °C / Reflux 6: 4-(N,N-dimethlyamino)pyridine; N-ethyl-N,N-diisopropylamine / dichloromethane / -10 - 0 °C View Scheme

1: 1,1'-carbonyldiimidazole / acetonitrile 2: hydrogenchloride; water / ethyl acetate 3: triethylamine / ethyl acetate; toluene 4: dirhodium(II) tetraoctanoate / acetone / Reflux 5: N-ethyl-N,N-diisopropylamine; zinc(II) iodide / acetone / -30 °C 6: N-ethyl-N,N-diisopropylamine / 1-methyl-pyrrolidin-2-one / -25 °C View Scheme

Multi-step reaction with 4 steps 1: 1,1'-carbonyldiimidazole / acetonitrile2: hydrogenchloride; water / ethyl acetate3: triethylamine / ethyl acetate; toluene4: dirhodium(II) tetraoctanoate / acetone / Reflux  

With  1,1'-carbonyldiimidazole in  tetrahydrofuran