1: 80 percent / 10 N aq. NaOH, NaBH4, chlorocobaloxime(III) / ethanol / 0.5 h / 50 - 60 °C / other 2-<(2-propynyl)oxy>ethyl bromides 2: 33 percent / chromium trioxide, pyridine / CH2Cl2 / 1 h / Heating View Scheme

sodium hydroxide; sodium tetrahydroborate; chlorocobaloxime(III) in ethanol T=50 - 60°C; 0.5 h;