1: Et3N, SO3-C5H5N, DMSO / Ambient temperature 2: CH2Cl2 / 24 h / Heating 3: 80 percent / aq. LiOH / methanol / 12 h / 45 °C 4: 34 percent / DDQ / dioxane / 0.08 h / Ambient temperature 5: 33 percent / Et3N, ClCOOEt / tetrahydrofuran / 0.08 h / 0 °C 6: 81 percent / Amberlyst 15 / methanol / 1 h / 45 °C View Scheme

With  diisobutylaluminium hydride in  hexane; toluene T=-78°C; 0.5 h;   

Multi-step reaction with 3 steps 1: Et3N, SO3-C5H5N, DMSO / 0.08 h / Ambient temperature2: CH2Cl2 / 6 h / Heating3: 89 percent / DIBAL-H / toluene; hexane / 0.5 h / -78 °C  

With  pyridine-SO3 complex; dimethyl sulfoxide; triethylamine  Ambient temperature;   

Multi-step reaction with 2 steps 1: Et3N, SO3-C5H5N, DMSO / Ambient temperature2: CH2Cl2 / 24 h / Heating  

Multi-step reaction with 3 steps 1: Et3N, SO3-C5H5N, DMSO / Ambient temperature2: CH2Cl2 / 24 h / Heating3: 80 percent / aq. LiOH / methanol / 12 h / 45 °C