Benzene → Methyl 2-oxo-1,2-dihydropyridine-3-carboxylate

Participants

Reaction Steps

A mixture containing 27.8 g of 1,2-dihydro-2-oxo-3-pyridinecarboxylic acid, 3.0 ml of concentrated sulfuric acid in 500 ml of methanol, and 300 ml of benzene are heated under reflux for 2.5 hours. A Dean-Stark trap is then attached, and the azeotrope collected is removed periodically in 25 ml fractions over a period of 28 hours. The remaining solvent is removed by evaporation under reduced pressure and the solid residue suspended in 500 ml of cold water. The suspension is filtered (from which unreacted starting material can be recovered) and the filtrate continuously extracted with methylene chloride. The extracts are concentrated under reduced pressure to yield the title compound as a white solid which, upon recrystallization from 1.4 L of benzene, yields 19.48 g (64%) of methyl 2-oxo-1,2-dihydro-3-pyridinecarboxylate: m.p. 148°-151° C.; NMR (DMSO-d6, 80 MHz) delta 3.72 (s, 3H), 6.25 (dd, 1H, J=7.1 Hz, J=6.3 Hz), 7.64 (dd, 1H, J=6.3 Hz, J=2.2 Hz), 8.03 (dd, 1H, J=7.1 Hz, J=2.2 Hz).

Provenance & Evidence