2,3-Dihydroxybutanedioic Acid → HCID 18004026, compound

Temperature

15 °C

A suspension of 2-(4-methylphenyl)-6-methylimidazo[1,2-a]-pyridine-3-acetic acid (60 g; 0.21 mols) in methylene chloride (600 mL) is added dropwise with thionyl chloride (27.4 g; 0.23 mols) adjusting the addition according to the gas evolution and keeping the temperature below 35° C. The resulting dark suspension is refluxed for 30 minutes, then cooled to 10÷15° C. and added with dimethylamine hydrochloride (98% titre, 20.5 g, 0.25 mols). Keeping the temperature below 15° C., triethylamine (83.5 g, 0.82 mols) is dropped therein. After one hour at room temperature, water is added (200 mL), the phases are separated and the lower organic phase is washed with a 5% sodium carbonate aqueous solution (200 mL) and subsequently with water (200 mL). The organic phase is concentrated to a residue, which is redissolved in methanol (600 mL) under reflux, and added with natural tartaric acid (16.5 g, 0.11 mols). The resulting solution is slowly cooled to 0° C. and the precipitated solid is filtered under nitrogen and washed with cold methanol (2×30 mL). The humid solid is taken up in methanol (400 mL), refluxed until dissolution and added with active carbon (3 g). The hot clear solution is filtered, then slowly cooled at 0° C. and the precipitated solid is filtered under nitrogen and washed with cold methanol (2×30 mL), then dried at 50° C. under vacuum to obtain Zolpidem tartrate (52.4 g, 99.6% titre, 99.0% HPLC purity, 65.2% yield).

1. additionthe addition
2. customthe temperature below 35° C
3. temperatureThe resulting dark suspension is refluxed for 30 minutes
4. additionis dropped
5. customthe phases are separated
6. washthe lower organic phase is washed with a 5% sodium carbonate aqueous solution (200 mL) and subsequently with water (200 mL)
7. concentrationThe organic phase is concentrated to a residue, which
8. dissolutionis redissolved in methanol (600 mL)
9. temperatureunder reflux
10. temperatureThe resulting solution is slowly cooled to 0° C.
11. filtrationthe precipitated solid is filtered under nitrogen
12. washwashed with cold methanol (2×30 mL)
13. temperaturerefluxed until dissolution
14. additionadded with active carbon (3 g)
15. filtrationThe hot clear solution is filtered
16. temperatureslowly cooled at 0° C.
17. filtrationthe precipitated solid is filtered under nitrogen
18. washwashed with cold methanol (2×30 mL)
19. customdried at 50° C. under vacuum

ORD record

ord-8319b554a6bd4e06983ef85a13cc82c2

Source dataset

uspto-grants-2002_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06384226B2