PRODUCTION OF 2-CARBOXY-BENZO-4-PYRONES

PURPOSE:To remarkably reduce the pollutant load of waste water and efficiently obtain the subject compounds by cyclizing 2-hydroxyacetophenones, an alcoholate and an oxalic acid diester with an acid in an aromatic hydrocarbon-based solvent. CONSTITUTION:A compound expressed by formula I (X is hydroxy, nitro, halogen, H or RCONH; R is a 1-20C alkyl, etc.) is reacted with an alcoholate and an oxalic acid diester in a solvent such as an alkylbezene, pyridine or chlorobenzene at -50 to +150 deg.C to provide a compound expressed by formula II (R' is a lower alkyl), which is, without isolation, cyclized with an acid selected from concentrated sulfuric acid, hydrogen chloride gas, methanesulfonic acid and glacial acetic acid at -50 to +100 deg.C to afford the objective compounds expressed by formula III.