1: H2; Lindlar catalyst; Et3N / hexane / 1 h 2: oxalyl chloride; DMSO; Et3N / CH2Cl2 / 0.67 h / -70 - -40 °C 3: benzene / 2 h / 60 °C 4: 82 percent / HMPA / tetrahydrofuran / 0.5 h / -78 °C 5: 90 percent / pyridinium p-toluenesulfonate / methanol / 1.5 h / 20 °C 6: 90 percent / 1N LiOH; CO2 / methanol; tetrahydrofuran / 2.5 h / 0 °C View Scheme