1.1: 25 percent / Bu4NHSO4; Oxone; K2CO3 / 4,5-O-Me2C-3-oxo-THP-2-spiro-4'-2',2'-Me2-1',3'-dioxolan / acetonitrile; various solvent(s); H2O / 1.5 h 2.1: 98 percent / NH4OH / tetrahydrofuran / 2 h / 130 °C 3.1: 80 mg / PPh3; DIAD / tetrahydrofuran / 17 h / Heating 4.1: DIAD; TFA / CH2Cl2; H2O / 1.5 h / 20 °C 4.2: 1.7 mg / KOH / CH2Cl2; H2O / 0.5 h / Heating 5.1: 92 percent / Na; NH3 / diethyl ether / 5 h / -78 - 20 °C View Scheme