1: 81 percent / silver oxide / acetone / 72 h / 20 °C 2: 75 percent / ammonia / tetrahydrofuran 3: 96 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C View Scheme

1: 75 percent / ammonia / tetrahydrofuran 2: 96 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C View Scheme

1: 1.) triethylamine, 2-mesitylenesulfonyl chloride, N,N-dimethylaminopyridine, 2.) 1,4-diazabicyclo<2.2.2>octane / 1.) dichloromethane, 30 min, 2.) dichloromethane, 60 min 2: 1.12 g / p-toluenesulfonic acid / CH2Cl2 / 0.03 h / 20 °C 3: 81 percent / silver oxide / acetone / 72 h / 20 °C 4: 75 percent / ammonia / tetrahydrofuran 5: 96 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C View Scheme

1: pyridine / 20 °C 2: triethylamine / CH2Cl2 / 0.25 h / 20 °C 3: 1.) triethylamine, 2-mesitylenesulfonyl chloride, N,N-dimethylaminopyridine, 2.) 1,4-diazabicyclo<2.2.2>octane / 1.) dichloromethane, 30 min, 2.) dichloromethane, 60 min 4: 1.12 g / p-toluenesulfonic acid / CH2Cl2 / 0.03 h / 20 °C 5: 81 percent / silver oxide / acetone / 72 h / 20 °C 6: 75 percent / ammonia / tetrahydrofuran 7: 96 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C View Scheme

1: triethylamine / CH2Cl2 / 0.25 h / 20 °C 2: 1.) triethylamine, 2-mesitylenesulfonyl chloride, N,N-dimethylaminopyridine, 2.) 1,4-diazabicyclo<2.2.2>octane / 1.) dichloromethane, 30 min, 2.) dichloromethane, 60 min 3: 1.12 g / p-toluenesulfonic acid / CH2Cl2 / 0.03 h / 20 °C 4: 81 percent / silver oxide / acetone / 72 h / 20 °C 5: 75 percent / ammonia / tetrahydrofuran 6: 96 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C View Scheme

sodium hydride 1) DMF, 0 deg C, 45 min, 2a) 0 deg C, 2.5 h, 2b) r.t., 1 h; Multistep reaction. Yields of byproduct given;

methanol; boron trifluoride Ring cleavage; 48 h; Heating;

tin(ll) chloride in methanol; ethylene glycol dimethyl ether 0.333333 h; Ambient temperature;

in N-methyl-acetamide; benzoic acid anhydride

in ethanol 1 h; Heating;