1: With borane-THF in tetrahydrofuran Heating / reflux; 2: With hydrogenchloride; water in tetrahydrofuran T=10 - 20°C; pH=2; 1 h;

hydrogenchloride; sodium hydroxide in tetrahydrofuran

1.1: water; sulfuric acid / 60 - 65 °C / Industry scale 1.2: 3.5 h / 50 - 98 °C 2.1: 1,3-dibromo-5,5-dimethyl-hydantoin / 1,2-dichloro-ethane / 7.5 h / 80 - 90 °C / Industry scale 3.1: potassium methanolate / toluene / -5 - 10 °C / Inert atmosphere; Industry scale 4.1: sodium hydroxide / isopropyl alcohol; methanol / 20 - 60 °C / Industry scale 4.2: 30 - 35 °C / Industry scale 5.1: urea / xylene / 6 h / Reflux 6.1: borane-THF / tetrahydrofuran / 1.25 h / 0 °C / Inert atmosphere; Steam bath 6.2: Cooling with ice View Scheme

1.1: sodium hydroxide / isopropyl alcohol; methanol / 20 - 60 °C / Industry scale 1.2: 30 - 35 °C / Industry scale 2.1: urea / xylene / 6 h / Reflux 3.1: borane-THF / tetrahydrofuran / 1.25 h / 0 °C / Inert atmosphere; Steam bath 3.2: Cooling with ice View Scheme

1.1: potassium methanolate / toluene / -5 - 10 °C / Inert atmosphere; Industry scale 2.1: sodium hydroxide / isopropyl alcohol; methanol / 20 - 60 °C / Industry scale 2.2: 30 - 35 °C / Industry scale 3.1: urea / xylene / 6 h / Reflux 4.1: borane-THF / tetrahydrofuran / 1.25 h / 0 °C / Inert atmosphere; Steam bath 4.2: Cooling with ice View Scheme

1.1: urea / xylene / 6 h / Reflux 2.1: borane-THF / tetrahydrofuran / 1.25 h / 0 °C / Inert atmosphere; Steam bath 2.2: Cooling with ice View Scheme

1.1: 1,3-dibromo-5,5-dimethyl-hydantoin / 1,2-dichloro-ethane / 7.5 h / 80 - 90 °C / Industry scale 2.1: potassium methanolate / toluene / -5 - 10 °C / Inert atmosphere; Industry scale 3.1: sodium hydroxide / isopropyl alcohol; methanol / 20 - 60 °C / Industry scale 3.2: 30 - 35 °C / Industry scale 4.1: urea / xylene / 6 h / Reflux 5.1: borane-THF / tetrahydrofuran / 1.25 h / 0 °C / Inert atmosphere; Steam bath 5.2: Cooling with ice View Scheme