sodium tetrahydroborate in methanol T=23°C;

1.1: diisopropylamine; n-BuLi / tetrahydrofuran; hexane / 1 h / -78 °C 1.2: 78 percent / tetrahydrofuran; hexane / 0.5 h / -78 °C 2.1: 84 percent / NaBH4 / methanol / 23 °C View Scheme