1: 90 percent / PPTS / 3 h / Ambient temperature 2: 80 percent / (n-Bu)4NF / tetrahydrofuran / 4 h / 40 °C 3: Et3N, SO3-C5H5N, DMSO / Ambient temperature 4: CH2Cl2 / 6 h / Heating 5: 76 percent / DIBAL-H / toluene; hexane / 0.5 h / -78 °C 6: Et3N, SO3-C5H5N, DMSO / Ambient temperature 7: CH2Cl2 / 24 h / Heating 8: aq. LiOH / methanol / 12 h / 45 °C 9: 88 percent / DDQ / dioxane / 0.08 h / Ambient temperature 10: Et3N, ClCOOEt / tetrahydrofuran / 0.08 h / 0 °C 11: Amberlyst 15 / methanol / 1 h / 45 °C View Scheme

Multi-step reaction with 2 steps 1: oxalyl chloride, DMSO, Et3N / CH2Cl2 2: 76 percent / tetrahydrofuran / 0.17 h / -35 °C  

Multi-step reaction with 3 steps 1: 90 percent / PPTS / 3 h / Ambient temperature2: 80 percent / (n-Bu)4NF / tetrahydrofuran / 4 h / 40 °C3: Et3N, SO3-C5H5N, DMSO / Ambient temperature  

Multi-step reaction with 10 steps 1: 90 percent / PPTS / 3 h / Ambient temperature2: 80 percent / (n-Bu)4NF / tetrahydrofuran / 4 h / 40 °C3: Et3N, SO3-C5H5N, DMSO / Ambient temperature4: CH2Cl2 / 6 h / Heating5: 76 percent / DIBAL-H / toluene; hexane / 0.5 h / -78 °C6: Et3N, SO3-C5H5N, DMSO / Ambient temperature7: CH2Cl2 / 24 h / Heating8: aq. LiOH / methanol / 12 h / 45 °C9: 88 percent / DDQ / dioxane / 0.08 h / Ambient temperature10: Et3N, ClCOOEt / tetrahydrofuran / 0.08 h / 0 °C