carbon monoxide; triphenylphosphine; palladium diacetate in acetonitrile T=70°C; P=4560 Torr; 12 h;

1: 85 percent / TBAF; isopropyl acetate / tetrahydrofuran / 20 °C 2: 87 percent / isopropyl acetate / tetrahydrofuran / 1 h / 20 °C 3: 4.55 g / DBU; isopropyl acetate / 1 h / 70 °C 4: 94 percent / PPh3; CO / Pd(OAc)2 / acetonitrile / 12 h / 70 °C / 4560 Torr View Scheme

1.1: tetrahydrofuran / 0.5 h / -5 °C 1.2: 81 percent / DDQ / tetrahydrofuran / 2 h / 20 °C 2.1: 85 percent / TBAF; isopropyl acetate / tetrahydrofuran / 20 °C 3.1: 87 percent / isopropyl acetate / tetrahydrofuran / 1 h / 20 °C 4.1: 4.55 g / DBU; isopropyl acetate / 1 h / 70 °C 5.1: 94 percent / PPh3; CO / Pd(OAc)2 / acetonitrile / 12 h / 70 °C / 4560 Torr View Scheme

1: 85 percent / TBAF; isopropyl acetate / tetrahydrofuran / 20 °C 2: 87 percent / isopropyl acetate / tetrahydrofuran / 1 h / 20 °C 3: 4.55 g / DBU; isopropyl acetate / 1 h / 70 °C 4: 94 percent / PPh3; CO / Pd(OAc)2 / acetonitrile / 12 h / 70 °C / 4560 Torr View Scheme

1: 87 percent / isopropyl acetate / tetrahydrofuran / 1 h / 20 °C 2: 4.55 g / DBU; isopropyl acetate / 1 h / 70 °C 3: 94 percent / PPh3; CO / Pd(OAc)2 / acetonitrile / 12 h / 70 °C / 4560 Torr View Scheme

1: CDCl3 2: 87 percent / TBAF; isopropyl acetate / tetrahydrofuran / 0.5 h / 20 °C 3: 87 percent / isopropyl acetate / tetrahydrofuran / 1 h / 20 °C 4: 4.55 g / DBU; isopropyl acetate / 1 h / 70 °C 5: 94 percent / PPh3; CO / Pd(OAc)2 / acetonitrile / 12 h / 70 °C / 4560 Torr View Scheme