4-hydroxy-2-methyl-2,3-dihydropyran-6-one

Conditions: temp:60.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 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. The mixture was cooled in an ice bath was formed The mixture was stirred overnight at room temperature was filtered concentrated purified by flash column chromatography

Conditions: temp:60.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 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. The mixture was cooled in an ice bath was formed The mixture was stirred overnight at room temperature was filtered concentrated purified by flash column chromatography

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 5.13 g (0.040 mole) of 4-hydroxy-5,6-dihydro-6-methyl-2-pyrone and 6.70 g (0.044 mole) of 1,8-diazabicyclo(5,4,0)-undecene (hereinafter referred to as DBU) in 100 ml of toluene was added dropwise 8.39 g (0.044 mole) of decanoyl chloride with stirring and cooling the reaction mixture in an ice-water bath. After termination of the dropwise addition, the mixture was stirred at room temperature for 7 hours. Water was added to the reaction mixture and the mixture was extracted with toluene. The extract was washed with 5% HCl and then with a saturated aqueous solution of sodium chloride, and dried over anhydrous magnesium sulfate. The solvent in the extract was evaporated under a reduced pressure, and the residue was subjected to silica gel column chromatography to purify the product, 4-dodecanoyloxy-6-methyl-5,6-dehydro-2-pyrone. To a solution of 4-dodecanoyloxy-6-methyl-5,6-dihydro-2-pyrone, thus obtained, in 20 ml of toluene was added 0.06 g of 4-pyrolidinopyridine. The mixture was refluxed for 3 hours and the solvent was removed by evaporation under a reduced pressure. The residue was purified by silica gel column chromatography to obtain 1.6 g (yield: 14%) of 3-decanoyl-6-methyltetrahydropyran-2,4-dione, m.p. 62°-63° C. cooling the reaction mixture in an ice-water bath After termination of the dropwise addition the mixture was stirred at room temperature for 7 hours the mixture was extracted with toluene The extract was washed with 5% HCl with a saturated aqueous solution of sodium chloride, and dried over anhydrous magnesium sulfate The solvent in the extract was evaporated under a reduced pressure to purify the product, 4-dodecanoyloxy-6-methyl-5,6-dehydro-2-pyrone

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 20.0 g (0.16 mole) of 4-hydroxy-6-methyl-2-pyrone in 250 ml of methanol was added 1.0 g of 5% palladium on carbon as the hydrogenation catalyst. Hydrogenation was carried out at room temperature under a pressure of 20 kg/cm2 for 7 hours. The catalyst was removed by filtration and the solvent was removed by evaporation under a reduced pressure. The precipitated crystal was recovered by filtration and recrystallized from ethanol to obtain 14.8 g (yield: 73%) of 4-hydroxy-5,6-dihydro-6-methyl-2-pyrone in the form of a crystal, m.p. 103°-104° C. The catalyst was removed by filtration the solvent was removed by evaporation under a reduced pressure The precipitated crystal was recovered by filtration recrystallized from ethanol

Conditions: temp:60.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 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. The mixture was cooled in an ice bath was formed The mixture was stirred overnight at room temperature was filtered concentrated purified by flash column chromatography