Hydrochloric Acid → HCID 178493810, compound

Temperature

35 °C

5-Methoxy-2-(tetrahydro-2H-pyran-2-yl) -3(2H)-pyridazinone (2035 g, 9.69 moles) and 2 L of methanol were added to a 22 L round bottomed flask equipped with a heating mantle, reflux condenser and mechanical stirrer. The mixture was warmed to 35° C. and 8 L of 6N HCl was added and then the mixture was heated to reflux for 2 h. The reaction mixture was then cooled slightly and transferred to a glycol cooled 22 L flask where the mixture was cooled further to 30° C. The mixture was made basic (pH 13-14) by cautious addition of 50% NaOH in small portions. The basic mixture was extracted with CH2Cl2 (4×3 L). The aqueous phase was then acidified with concentrated HCl (pH 1-2) to precipitate the product. The product was collected by vacuum filtration on a Buchner funnel. The product was dried to constant weight on a fluid bed dryer at 70° C. This afforded 798 g (65% yield) of 3-hydroxy-5-methoxypyridazine as a white solid which was recrystallized from methanol, mp=253°-255° C.

1. customequipped with a heating mantle
2. temperaturereflux condenser and mechanical stirrer
3. temperaturethe mixture was heated
4. temperatureto reflux for 2 h
5. temperatureThe reaction mixture was then cooled slightly
6. temperaturecooled 22 L flask where the mixture
7. temperaturewas cooled further to 30° C
8. extractionThe basic mixture was extracted with CH2Cl2 (4×3 L)
9. customto precipitate the product
10. filtrationThe product was collected by vacuum filtration on a Buchner funnel
11. customThe product was dried to constant weight on a fluid bed dryer at 70° C

ORD record

ord-9a171c7b6c1f47c5bacd4867730db4f1

Source dataset

uspto-grants-1997_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05623072