Dimethyl acetylenedicarboxylate → HCID 21314612, compound

Participants

Reaction Steps

To a solution of dimethylacetylenedicarboxylate (7.5 g) in dioxan (100 ml) containing `Triton 8` (10 drops) was added 5-hydroxy-7-methoxy-2,2-dimethylchroman (10.0 g) and the resulting mixture was warmed on a steam bath for 2 hours. A solution of sodium hydroxide (4.0 g) in water (20 ml) was added and heating was continued for 2 hours more. The organic solvent was removed and water (50 ml) was added to the residue and the mixture was acidified to give an oil which was extracted into ethylacetate. This solution was dried over MgSO4, filtered and the filtrate was evaporated to dryness. The oil so obtained was dissolved in concentrated H2SO4 (50 ml) and the solution was stirred at room temperature for 30 minutes, poured into ice and extracted with ethyl acetate. This solution was washed with water, dried (MgSO4), filtered and evaporated to dryness. The oil so produced was triturated with ethyl acetate, cooled to 0°, and the solid produced was filtered and dried. The solid was crystallised from ethanol to give 8,9-dihydro-5-methoxy-8,8-dimethyl-4-oxo-4H,10H-benzo[1,2-b:3,4-b']dipyran-2-carboxylic acid as a white solid (3.4 g, 23%) mp 225°-6°.

Provenance & Evidence