Maltol → 4-Pyridinone,3-OH-2-Me

Participants

Reaction Conditions

Reaction Steps

A 500-mL high-pressure reaction vessel equipped with a magnetic stir bar and a thermometer was charged with maltol (20 g, 0.16 mol), ethanol (40 mL) and ammonium hydroxide solution (28.0-30.0%, 35 mL, 0.52 mol). The reaction vessel was sealed and heated at 66° C. for 2.5 h. HPLC analysis (HPLC Method 1, Example 24) indicated that only 26% of product (peak percent area) was formed. Another 30 mL of conc. ammonium hydroxide (28.0-30.0%, 0.45 mol) was added, and the resulting mixture was sealed and heated to 75° C. for overnight. Upon cooling, a solid separated, and it was collected by suction filtration (8.7 g). HPLC analysis of the solid indicated presence of the desired product and maltol in about 4/1 ratio. The solid was slurried in methanol (30 mL), and the resulting mixture was stirred. The solid 3-hydroxy-2-methyl-1H-pyridin-4-one was collected by suction filtration (4.8 g, 24% yield, HPLC purity (peak percent area): 99.7% at λ=280 nm). 1H NMR (DMSO-d6) δ ppm: 11.6 (br s, 1H), 7.40 (d, J=6.8 Hz, 1H), 6.09 (d, J=6.8 Hz, 1H), 2.17 (s, 3H).

Provenance & Evidence