Methylamine → Ethyl 4-hydroxy-1,5-dimethyl-6-oxo-1,6-dihydropyridine-3-carboxylate

Temperature

135 °C

Triethyl orthoformate (3.85 mL, 23.12 mmol) and acetic anhydride (4.37 mL, 46.25 mmol) were added to 2-methyl-3-oxo-pentanedioic acid diethyl ester (Caliskan et al Aust. J. Chem. 1999, 52 (11), 1013-1020) (5.0 g, 23.1 mmol) and the reaction mixture heated to 135° C. After 1 hour, the reaction mixture was cooled to room temperature and concentrated under reduced pressure. The residue was cooled to 0° C. and methylamine (40% in water, 5.0 mL, 57.81 mmol) was added with stirring. Water (20 mL) was added and the reaction mixture stirred for 16 hours. The reaction mixture was extracted with ethyl acetate and the aqueous layer acidified to pH 2 with 10% aqueous HCl. The acidified aqueous layer was extracted with ethyl acetate. The combined organic extracts were dried (MgSO4) and concentrated to give a solid. Trituration with diethyl ether yielded 4.88 g (55%) clean desired product. 4-Hydroxy-1,5-dimethyl-6-oxo-1,6-dihydropyridine-3-carboxylic acid ethyl ester was carried forward as described in Example 1, Steps B-D. MS APCI (−) m/z 353, 355 (M−, Br pattern) detected; 1H NMR (400 mHz, CD3OD) δ 8.49 (s, 1H), 7.36 (dd, 1H), 7.24 (dd, 1H), 6.71 (m, 1H), 3.60 (s, 3H), 1.68 (s, 3H).

1. temperaturethe reaction mixture was cooled to room temperature
2. concentrationconcentrated under reduced pressure
3. temperatureThe residue was cooled to 0° C.
4. stirringthe reaction mixture stirred for 16 hours
5. extractionThe reaction mixture was extracted with ethyl acetate
6. extractionThe acidified aqueous layer was extracted with ethyl acetate
7. dry with materialThe combined organic extracts were dried (MgSO4)
8. concentrationconcentrated
9. customto give a solid

ORD record

ord-ce3922ee628147f3a2c5f74c0fc4da1d

Source dataset

uspto-grants-2009_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07598383B2