hydrogen; palladium on activated charcoal in acetic acid T=70 - 80°C; P=15001.2 Torr;

1.1: Et3N; ClCOOEt / tetrahydrofuran / 10 h / 20 °C 1.2: 90 percent / NaBH4 / tetrahydrofuran; H2O / 5 h / 20 °C 2.1: 78 percent / pyridinium chloroformate/SiO2 / CH2Cl2 / 1.5 h / 20 °C 3.1: NaH / dimethylsulfoxide / cooling 3.2: 100 percent / dimethylsulfoxide / 1 h / 20 °C View Scheme

1: With sulfuric acid T=20 - 60°C; 3.5 h; 2: With water; sodium hydrogencarbonate in methanol

1.1: sodium tetrahydroborate; sulfuric acid / diethyl ether; tetrahydrofuran / 0.75 h / 0 - 35 °C 1.2: pH 7 2.1: sodium hydrogencarbonate / iodine; 2,2,6,6-tetramethyl-1-piperidinyloxy, free radical / dichloromethane / 0.17 h / 20 °C 2.2: 24 h / 20 - 25 °C 3.1: sodium hydride / dimethyl sulfoxide / 0.5 h 3.2: 1 h / 20 - 25 °C 4.1: isopropyl alcohol / Reflux 5.1: ammonium formate / palladium 10 on activated carbon / methanol / 3 h / Reflux View Scheme

1: 6-fluoro-3,4-dihydro-2H-1-benzopyran-2-carboxylic acid With chloroformic acid ethyl ester; triethylamine in dichloromethane T=0 - 5°C; 1.5 - 2.25 h; 2: piperidine in dichloromethane T=0 - 5°C; 2 - 2.25 h; Product distribution / selectivity;

1: With sodium tetrahydroborate; sulfuric acid in tetrahydrofuran; diethyl ether T=0 - 35°C; 0.75 h; 2: With sodium hydroxide in water pH=7; Product distribution / selectivity;

1.1: sodium tetrahydroborate; sulfuric acid / diethyl ether; tetrahydrofuran / 0.75 h / 0 - 35 °C 1.2: pH 7 2.1: sodium hydrogencarbonate / iodine; 2,2,6,6-tetramethyl-1-piperidinyloxy, free radical / dichloromethane / 0.17 h / 20 °C 2.2: 24 h / 20 - 25 °C 3.1: sodium hydride / dimethyl sulfoxide / 0.5 h 3.2: 1 h / 20 - 25 °C 4.1: isopropyl alcohol / Reflux 5.1: ammonium formate / palladium 10 on activated carbon / methanol / 3 h / Reflux 6.1: hydrogenchloride / methanol / 25 - 35 °C View Scheme

1.1: Et3N; ClCOOEt / tetrahydrofuran / 10 h / 20 °C 1.2: 90 percent / NaBH4 / tetrahydrofuran; H2O / 5 h / 20 °C 2.1: 78 percent / pyridinium chloroformate/SiO2 / CH2Cl2 / 1.5 h / 20 °C View Scheme