sodium tetrahydroborate in ethanol T=20°C; 2 h;

1: 68 percent / imidazole / dimethylformamide / 3 h / 20 °C 2: 88 percent / imidazole; 4-dimethylaminopyridine / CH2Cl2 / 17 h / 20 °C 3: 76 percent / pyridinium p-toluenesulfonate / ethanol / 66 h / 20 °C View Scheme

1: 68 percent / imidazole / dimethylformamide / 3 h / 20 °C 2: 88 percent / imidazole; 4-dimethylaminopyridine / CH2Cl2 / 17 h / 20 °C 3: 76 percent / pyridinium p-toluenesulfonate / ethanol / 66 h / 20 °C 4: 86 percent / pyridine / 72 h / 20 °C 5: 96 percent / tetrabutylammonium fluoride / tetrahydrofuran / 72 h / 20 °C 6: 56 percent / oxalyl chloride; DMSO; Et3N / CH2Cl2 / 0.5 h / -65 °C View Scheme

1: 68 percent / imidazole / dimethylformamide / 3 h / 20 °C 2: 88 percent / imidazole; 4-dimethylaminopyridine / CH2Cl2 / 17 h / 20 °C 3: 76 percent / pyridinium p-toluenesulfonate / ethanol / 66 h / 20 °C 4: 86 percent / pyridine / 72 h / 20 °C 5: 96 percent / tetrabutylammonium fluoride / tetrahydrofuran / 72 h / 20 °C View Scheme