1: 66 percent / tetramethylammonium triacetoxyborohydride / acetonitrile; acetic acid / 5 h / -5 - 0 °C 2: 70 percent / 4-dimethylaminopyridine / dimethylformamide / 168 h / 50 °C 3: 57 percent / 2,6-lutidine / CH2Cl2 / 0.5 h / -70 °C 4: 69 percent / N-methyl-morpholine-N-oxide, tetrapropylammonium-perrhutenate / CH2Cl2 / 12 h / Ambient temperature; presence of 4 A mol sieve 5: 88 percent / 1 N HCl / acetonitrile / 0.5 h / Ambient temperature View Scheme

1: 66 percent / tetramethylammonium triacetoxyborohydride / acetonitrile; acetic acid / 5 h / -5 - 0 °C 2: 70 percent / 4-dimethylaminopyridine / dimethylformamide / 168 h / 50 °C View Scheme

Multi-step reaction with 3 steps 1: 66 percent / tetramethylammonium triacetoxyborohydride / acetonitrile; acetic acid / 5 h / -5 - 0 °C2: 70 percent / 4-dimethylaminopyridine / dimethylformamide / 168 h / 50 °C3: 57 percent / 2,6-lutidine / CH2Cl2 / 0.5 h / -70 °C