1: hydrogenchloride; water / 20 - 70 °C 2: acetic acid / methanol / 0 - 30 °C 3: isopentyl nitrite / acetonitrile / 30 - 60 °C 4: N-ethyl-N,N-diisopropylamine / acetonitrile / 25 - 35 °C 5: lithium borohydride / tetrahydrofuran / -10 - 20 °C View Scheme