diisobutylaluminium hydride in diethyl ether T=-78°C;

1.1: 91 percent / DIBAL / diethyl ether; tetrahydrofuran / 2 h / -78 - -20 °C 2.1: n-BuLi / diethyl ether; hexane / 0.83 h / -78 - -23 °C 2.2: ClTi(OiPr)3 / diethyl ether; hexane / 0.25 h / -78 - -20 °C 2.3: 13 percent / diethyl ether; hexane / 4 h / -110 - -78 °C 3.1: 93 percent / aq. HCl / tetrahydrofuran / 0.5 h / 20 °C 4.1: DIBAL-H / tetrahydrofuran; toluene / 3.5 h / -78 °C 4.2: 86 percent / aq. HCl / tetrahydrofuran / -78 - 20 °C View Scheme

1.1: 91 percent / DIBAL / diethyl ether; tetrahydrofuran / 2 h / -78 - -20 °C 2.1: n-BuLi / diethyl ether; hexane / 0.83 h / -78 - -23 °C 2.2: ClTi(OiPr)3 / diethyl ether; hexane / 0.25 h / -78 - -20 °C 2.3: 72 percent / diethyl ether; hexane / 4 h / -110 - -78 °C 3.1: 91 percent / aq. HCl / tetrahydrofuran / 0.5 h / 20 °C 4.1: DIBAL-H / tetrahydrofuran; toluene / 3.5 h / -78 °C 4.2: 84 percent / aq. HCl / tetrahydrofuran / -78 - 20 °C View Scheme