acetic acid Cyclization; 6 h; Heating;

1: oxalyl chloride / CH2Cl2; dimethylformamide / 1 h / 0 °C 2: CH2Cl2 / 1 h / Ambient temperature 3: 93 percent / TFA / 10 - 15 °C 4: 1.) 4-formyl-1-methylpyridinium benzenesulfonate, 2.) DBU, 3.) aq. oxalic acid / 1) CH2Cl2, DMF, room temperature; 2) 5 min; 3) cooling, 0.5 - 1 h 5: 1.) Jones reagent, 2.) aq. HCl / 1) room temperature, acetone; 2) heating 6: 85 percent / 0.5 h / 170 °C View Scheme

1: 94 percent / aq. alkali 2: oxalyl chloride / CH2Cl2; dimethylformamide / 1 h / 0 °C 3: CH2Cl2 / 1 h / Ambient temperature 4: 93 percent / TFA / 10 - 15 °C 5: 1.) 4-formyl-1-methylpyridinium benzenesulfonate, 2.) DBU, 3.) aq. oxalic acid / 1) CH2Cl2, DMF, room temperature; 2) 5 min; 3) cooling, 0.5 - 1 h 6: 1.) Jones reagent, 2.) aq. HCl / 1) room temperature, acetone; 2) heating 7: 85 percent / 0.5 h / 170 °C View Scheme

1: 84 percent / aq. NaOH, aq. Na2CO3 / 3 h / 0 - 5 °C 2: 82 percent / aq. NaOH, KMnO4 / 2 h / 5 - 10 °C 3: 83 percent / H2, 60percent aq. AcOH / 10percent Pd/C / 2 h 4: 68 percent / 20percent aq. AcOH / 3 h / Heating View Scheme

1: 83 percent / H2, 60percent aq. AcOH / 10percent Pd/C / 2 h 2: 68 percent / 20percent aq. AcOH / 3 h / Heating View Scheme

1: 82 percent / aq. NaOH, KMnO4 / 2 h / 5 - 10 °C 2: 83 percent / H2, 60percent aq. AcOH / 10percent Pd/C / 2 h 3: 68 percent / 20percent aq. AcOH / 3 h / Heating View Scheme

1: 1.) Jones reagent, 2.) aq. HCl / 1) room temperature, acetone; 2) heating 2: 85 percent / 0.5 h / 170 °C View Scheme

1: 1.) 4-formyl-1-methylpyridinium benzenesulfonate, 2.) DBU, 3.) aq. oxalic acid / 1) CH2Cl2, DMF, room temperature; 2) 5 min; 3) cooling, 0.5 - 1 h 2: 1.) Jones reagent, 2.) aq. HCl / 1) room temperature, acetone; 2) heating 3: 85 percent / 0.5 h / 170 °C View Scheme

1: 93 percent / TFA / 10 - 15 °C 2: 1.) 4-formyl-1-methylpyridinium benzenesulfonate, 2.) DBU, 3.) aq. oxalic acid / 1) CH2Cl2, DMF, room temperature; 2) 5 min; 3) cooling, 0.5 - 1 h 3: 1.) Jones reagent, 2.) aq. HCl / 1) room temperature, acetone; 2) heating 4: 85 percent / 0.5 h / 170 °C View Scheme

1: 40.4 percent / KMnO4, 1 M aq. H2SO4, 50percent aq. AcOH / 0.25 h / 10 - 15 °C 2: 81.5 percent / 1 N aq. HCl / 3 h / Heating 3: 68 percent / 20percent aq. AcOH / 3 h / Heating View Scheme