1.1: 94 percent / KHMDS / tetrahydrofuran; toluene / 1 h / -78 °C 2.1: O3 / CH2Cl2 / -78 °C 2.2: 35 percent / DIBALH / CH2Cl2 3.1: 85 percent / Pd(OAc)2; PPh3; Et3N / methanol; dimethylformamide / 3.5 h 4.1: 5.6 mg / DIBAL-H / diethyl ether; hexane / -78 - 20 °C 5.1: 55 percent / (COCl)2; DMSO View Scheme