1,3-Cyclohexanedione → 2-Methyl-2,6,7,8-tetrahydro-chromen-5-one

A solution of crotonaldehyde (72.74 g, 1.04 mol) in 500 mL of pyridine was added to 1,3-cyclohexanedione (100 g, 0.892 mol) in 500 mL of pyridine and the mixture was heated to reflux under a nitrogen atmosphere for 1 hour. The mixture was cooled to room temperature and then filtered through magnesium sulfate (328 g). The filtrate was concentrated to dryness and the residue was partitioned between water and diethyl ether. The aqueous phase was extracted with diethyl ether and the combined diethyl ether layers were washed with 10% hydrochloric acid (3×150 mL). The diethyl ether layer was then washed with water to neutrality, dried (MgSO4), filtered and the filtrate concentrated to dryness. The residue was purified by Kugelrohr distillation (bp 109°-112° C. (1 to 2 mm)) to give 2-methyl-5,6,7,8-tetrahydro-2H-1-benzopyran-5-one (48.2 g, 0.294 mol) as an oil.

1. temperaturethe mixture was heated
2. temperatureto reflux under a nitrogen atmosphere for 1 hour
3. filtrationfiltered through magnesium sulfate (328 g)
4. concentrationThe filtrate was concentrated to dryness
5. customthe residue was partitioned between water and diethyl ether
6. extractionThe aqueous phase was extracted with diethyl ether
7. washthe combined diethyl ether layers were washed with 10% hydrochloric acid (3×150 mL)
8. washThe diethyl ether layer was then washed with water to neutrality
9. dry with materialdried (MgSO4)
10. filtrationfiltered
11. concentrationthe filtrate concentrated to dryness
12. distillationThe residue was purified by Kugelrohr distillation (bp 109°-112° C. (1 to 2 mm))

ORD record

ord-fd7360e351f04c3db56a441b6cfe3775

Source dataset

uspto-grants-1996_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05492914