Acetic Acid → 3-Acetyl-4-hydroxy-6-methyl-5,6-dihydro-pyran-2-one

Participants

Reaction Conditions

Reaction Steps

4-Hydroxy-6-methyl-5,6-dihydro-pyran-2-one (2 g, 15.6 mmol) was combined with methylene chloride (50 mL) in a 250 mL flask and then acetic acid (17.5 M, 2 eq, 31 mmol, 1.77 mL) was added to the mixture. The mixture was cooled in an ice bath and then dicyclohexylcarbodiimide (1.3 eq, 20.3 mmol, 4.19 g) was added portionwise, followed by the addition of 4-(dimethylamino)pyridine (0.05 eq, 0.78 mmol, 88 mg) to the mixture. A sufficient amount of methylene chloride was added to ensure easy stirring and the reaction was monitored by TLC (silica gel, hexane-ethyl acetate-methylene chloride-acetone (3:3:3:1 v/v)), HPLC and LCMS as the intermediate acetic acid 2-methyl-6-oxo-3,6-dihydro-2H-pyran-4-yl ester was formed. The mixture was stirred overnight at room temperature and then toluene (20 ml) was added. The mixture was heated to 60° C. and after 48 hours the mixture was filtered, concentrated and purified by flash column chromatography to provide 3-acetyl-4-hydroxy-6-methyl-5,6-dihydro-pyran-2-one (1.02 g, 38%) as a white solid, mp 96-98° C. (lit., mp 97-98° C.). LCMS: MH+ 171.0.

Provenance & Evidence