Phthalaldehydic acid → 1-oxo-1H-isochromene-3-carboxylic acid

Participants

Reaction Steps

A mixture of 2-carboxybenzaldehyde (20.0g), diethyl bromomalonate (20.0g) and anhydrous potassium carbonate (20.0g) in ethyl methylketone (200ml.) was heated under reflux, with stirring, for 5 hours. The cooled mixture was evaporated to dryness and water (300ml.) added to the residue. After extraction with a mixture of ether-chloroform, the organic extracts were washed with water, dried and evaporated to dryness. The residual solid was heated under reflux with a mixture of concentrated hydrochloric acid (360ml.) -- acetic acid (240ml.) for 2 hours. After cooling, the mixture was poured into iced water (1,200ml.). Filtration gave the product as a white solid, m.p. 241°-2° (lit mp. 239°-240°), (Found: C, 62.87; H, 3.39. C10H6O4 requires C, 63.16; H 3.18).

Provenance & Evidence