Acetone → 6-methoxy-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran-4-one

Participants

Reaction Steps

A mixture of 48.9 g (0.294 mole) 2-hydroxy-5-methoxyacetophenone, 32 mL (0.441 mole) acetone and 12 mL (0.147 mmole) pyrrolidine in 300 mL toluene was stirred at room temperature for 3 hours, then refluxed over a Dean-Stark trap for 3 hours. An additional 32 mL (0.441 mole) acetone and 12 mL (0.147 mole) pyrrolidine was added and the mixture again refluxed over the Dean-Stark trap for 18 hours. The mixture was concentrated, poured into water, basified, and extracted with ether. The ether extract was, washed with 1N KOH, water and brine and then dried (MgSO4) and concentrated to give an oil. Flash chromatography on silica gel with 20% ethyl acetate in hexanes afforded a solid. Recrystallization from ether/hexanes yielded 32.0 g (53%) of pure product. mp 71°-73° C. Analysis calculated for C12H14O3 : C, 69.89; H, 6.84. Found: C, 69.85; H, 7.08.

Provenance & Evidence