1: ethanol / 1.) 1 h, room temp. 2.) 2 h, reflux 2: 86.3 percent / pyridine / 1.) 0 deg C, 2 h, 2.) 3 h, room temp. 3: 83.6 percent / dimethylsulfoxide, oxalyl chloride / CH2Cl2 / 2 h / -70 °C 4: 17.4 percent / Me3Al, 2,4,6-tri-tert-butylphenol / hexane; toluene; diethyl ether / 1.5 h / -78 °C 5: 94.5 percent / tetra-n-butylammonium fluoride / tetrahydrofuran / 0.33 h 6: 95.6 percent / NH3 / methanol / 48 h / 100 °C View Scheme