1.1: DMSO; TFAA / CH2Cl2 / 2 h / -78 °C 1.2: 71 percent / Et3N / CH2Cl2 / 1 h / -78 - 20 °C 2.1: 32 percent / NaBH3CN; HCO2NH4; molecular sieves (3A) / methanol / 24 h / 20 °C View Scheme

manganese(IV) oxide in dichloromethane 24 h;