citric acid in methanol; ethyl acetate; toluene

1: With lithium aluminium tetrahydride in tetrahydrofuran T=0 - 20°C; 1 h; 2: With hydrogenchloride in tetrahydrofuran; water Product distribution / selectivity;

1: 3,4-dihydro-6-methyl-4-phenyl-2H-benzopyran-2-one With diisobutylaluminium hydride in toluene T=-25°C; 5 h; 2: With citric acid in water; ethyl acetate; toluene T=20°C; 3: diisopropylamine With hydrogen; 5-palladium/activated carbon in methanol T=48°C; P=3800.26 Torr; 12 h;

1.1: potassium carbonate / acetone / Reflux 2.1: potassium hydroxide; water / methanol / Inert atmosphere; Reflux 2.2: pH 1 - 2 3.1: toluene / 0 - 10 °C 3.2: 50 - 60 °C 4.1: sodium tetrahydroborate; boron trifluoride diethyl etherate / tetrahydrofuran / 31 - 35 °C 4.2: 30 - 65 °C 5.1: isopropyl alcohol; water / Reflux 6.1: sodium carbonate / dichloromethane; water 6.2: 14 - 20 °C 7.1: hydrogenchloride; sodium tetrahydroborate / water / 32 - 38 °C 7.2: Reflux 8.1: sodium hydroxide; sodium carbonate / dichloromethane; water 8.2: Raney nickel View Scheme

1.1: potassium carbonate / acetone / Reflux 2.1: potassium hydroxide; water / methanol / Inert atmosphere; Reflux 2.2: pH 1 - 2 3.1: toluene / 0 - 10 °C 3.2: 50 - 60 °C 4.1: sodium tetrahydroborate; boron trifluoride diethyl etherate / tetrahydrofuran / 31 - 35 °C 4.2: 30 - 65 °C 5.1: isopropyl alcohol; water / Reflux 6.1: sodium carbonate / dichloromethane; water 6.2: 14 - 20 °C 7.1: hydrogenchloride; sodium tetrahydroborate / water / 32 - 38 °C 7.2: Reflux 8.1: sodium hydroxide; sodium carbonate / dichloromethane; water 8.2: Raney nickel 9.1: triethylamine / dichloromethane / 0.75 h / 0 - 20 °C View Scheme

1: 3,4-dihydro-6-methyl-4-phenyl-2H-benzopyran-2-one With water; sodium hydroxide T=60 - 65°C; 2 h; 2: dimethyl sulfate in water T=20°C; 3 h;

1.1: potassium carbonate / methanol / 10 h / 55 - 60 °C 2.1: sodium bis(2-methoxyethoxy)aluminium dihydride / toluene / 3 h / -5 - 5 °C / Inert atmosphere 3.1: triethylamine / dichloromethane / 3 h / 0 - 10 °C / Inert atmosphere 4.1: sodium iodide / acetonitrile / 4 h / 100 °C / Autoclave 4.2: Inert atmosphere 5.1: boron tribromide / dichloromethane / Inert atmosphere 5.2: 0.5 h / 30 - 35 °C View Scheme

1: 3,4-dihydro-6-methyl-4-phenyl-2H-benzopyran-2-one With diisobutylaluminium hydride in toluene T=-25°C; 5 h; 2: With citric acid in water; ethyl acetate; toluene T=20°C; 3: diisopropylamine With hydrogen; 5-palladium/activated carbon in methanol T=48°C; P=3800.26 Torr; 12 h;

1: potassium carbonate / methanol / 10 h / 55 - 60 °C 2: sodium bis(2-methoxyethoxy)aluminium dihydride / toluene / 3 h / -5 - 5 °C / Inert atmosphere View Scheme

2,3-dicyano-5,6-dichloro-p-benzoquinone in 1,4-dioxane T=110°C; 12 h;