1,3-bis(oxan-2-yloxy)propan-2-one

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

Procedure: 9.0 g of dihydroxyacetone dimer, 21.0 g of 3,4-dihydro-2H-pyran and a catalytic amount of p-toluenesulfonic acid were added to 70 ml of dichloromethane and stirred under ice-cooling for 3 hours. After the completion of the reaction, 150 ml of diethyl ether was added thereto. The mixture was then washed with a saturated aqueous solution of sodium hydrogencarbonate and dried over anhydrous magnesium sulfate. After distilling off the solvent, the oily residue thus obtained was subjected to chromatography wherein silica gel was employed as a carrier while hexane/ethyl acetate was employed as a mobile phase. Thus 16.5 g of 1,3-bis(2-tetrahydro-pyranyloxy)propan-2-one was obtained as a colorless viscous liquid. cooling for 3 hours was added The mixture was then washed with a saturated aqueous solution of sodium hydrogencarbonate dried over anhydrous magnesium sulfate After distilling off the solvent the oily residue thus obtained

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

Procedure: 9 g of 2,5-dihydroxy-1,4-dioxane-2,5-dimethanol were introduced into 60 ml of dioxane and the suspension was taken to about 70° C. for 15 minutes, then taken to ambient temperature. Then, 20 ml of 3,4-dihydro-2H-pyran and 300 mg of monohydrated p-toluene sulfonic acid were added. The temperature was held at about 40° C. and then the reaction medium stood overnight at ambient temperature. It was then poured into a mixture of 300 ml of a saturated solution of sodium bicarbonate+10 ml of triethylamine and extraction was carried out 4 times with methylene chloride. The organic phase was washed with salt water and dried. After purification by passing through silica with ethyl cycloacetate/triethylamine: 8/2 as eluant, 17 g of the expected product (pale yellow syrup) were obtained. taken to ambient temperature was held at about 40° C. the reaction medium stood overnight at ambient temperature The organic phase was washed with salt water dried After purification

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

Procedure: 5.6 g of the product of Stage 1 were introduced into 8 ml of ammonium hydroxide and the mixture was brought to about -5° C. 1.58 g of ammonium chloride and 1.23 g of sodium cyanide were added successively and the mixture was allowed to return to ambient temperature for about 40 minutes, then heated to 40° C.±5° C. with stirring overnight. The reaction medium was returned to ambient temperature and extraction was carried out 3 times with chloroform. The organic phase was washed with salt water and dried. After purification on silica with ethyl cycloacetate/triethylamine; 3/7 as eluant, 4.41 g of the expected product (pale yellow syrup) were obtained. was brought to about -5° C heated to 40° C.±5° C. was returned to ambient temperature extraction The organic phase was washed with salt water dried After purification on silica with ethyl cycloacetate/triethylamine

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

Procedure: 9 g of 2,5-dihydroxy-1,4-dioxane-2,5-dimethanol were introduced into 60 ml of dioxane and the suspension was taken to about 70° C. for 15 minutes, then taken to ambient temperature. Then, 20 ml of 3,4-dihydro-2H-pyran and 300 mg of monohydrated p-toluene sulfonic acid were added. The temperature was held at about 40° C. and then the reaction medium stood overnight at ambient temperature. It was then poured into a mixture of 300 ml of a saturated solution of sodium bicarbonate +10 ml of triethylamine and extraction was carried out 4 times with methylene chloride. The organic phase was washed with salt water and dried. After purification by passing through silica with ethyl cycloacetate/triethylamine: 8/2 as eluant, 17 g of the expected product (pale yellow syrup) were obtained. taken to ambient temperature was held at about 40° C. the reaction medium stood overnight at ambient temperature The organic phase was washed with salt water dried After purification

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

Procedure: 9 g of 2,5-dihydroxy-1,4-dioxane-2,5-dimethanol were introduced into 60 ml of dioxane and the suspension was taken to about 70° C. for 15 minutes, then taken to ambient temperature. Then, 20 ml of 3,4-dihydro-2H-pyran and 300 mg of monohydrated p-toluene sulfonic acid were added. The temperature was held at about 40° C. and then the reaction medium stood overnight at ambient temperature. It was then poured into a mixture of 300 ml of a saturated solution of sodium bicarbonate +10 ml of triethylamine and extraction was carried out 4 times with methylene chloride. The organic phase was washed with salt water and dried. After purification by passing through silica with ethyl cycloacetate/triethylamine: 8/2 as eluant, 17 g of the expected product (pale yellow syrup) were obtained. taken to ambient temperature was held at about 40° C. the reaction medium stood overnight at ambient temperature The organic phase was washed with salt water dried After purification

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

Procedure: 5.6 g of the product obtained in Stage 1 above is introduced into 8 ml of ammonium hydroxide, the mixture is taken to about -5° C. and 1.58 g of ammonium chloride and 1.23 g of sodium cyanide are added successively and the reaction medium is left to rise to ambient temperature for about 40 minutes then heated at 40° C.±5° C. under agitation overnight. It is returned to ambient temperature and extraction is carried out 3 times with chloroform, the organic phase is washed with salt water and dried. After purification on silica, eluting with cyclohexane-ethyl acetate: 3-7 with 0.5% of triethylamine, 4.41 g of expected product (pale yellow syrup) is obtained. is taken to about -5° C. the reaction medium is left then heated at 40° C.±5° C. under agitation overnight is returned to ambient temperature extraction the organic phase is washed with salt water dried After purification on silica eluting with cyclohexane-ethyl acetate

Conditions: temp:40.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 9 g of 2,5-dihydroxy-1,4-dioxane-2,5-dimethanol is introduced into 60 ml of dioxane and the suspension is taken to about 70° C. for 15 minutes then returned to ambient temperature. 20 ml of 3,4-dihydro 2H-pyran and 300 mg of monohydrated paratoluene sulphonic acid are then added and the temperature is maintained at about 40° C. then the whole is left for 16 hours at ambient temperature. The reaction medium is poured into a mixture of 300 ml of saturated sodium bicarbonate solution +10 ml of triethylamine and extraction is carried out 4 times with methylene chloride. The organic phase is washed with salt water and dried. After purification by passage through silica, eluting with cyclohexane-ethyl acetate: 8-2 with 0.5% of triethylamine, 17 g of expected product (pale yellow syrup) is obtained. then returned to ambient temperature the whole is left for 16 hours at ambient temperature The organic phase is washed with salt water dried After purification by passage through silica eluting with cyclohexane-ethyl acetate

Conditions: temp:40.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 9 g of 2,5-dihydroxy-1,4-dioxane-2,5-dimethanol is introduced into 60 ml of dioxane and the suspension is taken to about 70° C. for 15 minutes then returned to ambient temperature. 20 ml of 3,4-dihydro 2H-pyran and 300 mg of monohydrated paratoluene sulphonic acid are then added and the temperature is maintained at about 40° C. then the whole is left for 16 hours at ambient temperature. The reaction medium is poured into a mixture of 300 ml of saturated sodium bicarbonate solution +10 ml of triethylamine and extraction is carried out 4 times with methylene chloride. The organic phase is washed with salt water and dried. After purification by passage through silica, eluting with cyclohexane-ethyl acetate: 8-2 with 0.5% of triethylamine, 17 g of expected product (pale yellow syrup) is obtained. then returned to ambient temperature the whole is left for 16 hours at ambient temperature The organic phase is washed with salt water dried After purification by passage through silica eluting with cyclohexane-ethyl acetate

Conditions: temp:40.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 9 g of 2,5-dihydroxy-1,4-dioxane-2,5-dimethanol is introduced into 60 ml of dioxane and the suspension is taken to about 70° C. for 15 minutes then returned to ambient temperature. 20 ml of 3,4-dihydro 2H-pyran and 300 mg of monohydrated paratoluene sulphonic acid are then added and the temperature is maintained at about 40° C. then the whole is left for 16 hours at ambient temperature. The reaction medium is poured into a mixture of 300 ml of saturated sodium bicarbonate solution +10 ml of triethylamine and extraction is carried out 4 times with methylene chloride. The organic phase is washed with salt water and dried. After purification by passage through silica, eluting with cyclohexane-ethyl acetate: 8-2 with 0.5% of triethylamine, 17 g of expected product (pale yellow syrup) is obtained. then returned to ambient temperature the whole is left for 16 hours at ambient temperature The organic phase is washed with salt water dried After purification by passage through silica eluting with cyclohexane-ethyl acetate

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

Procedure: A solution of 0.14 moles of methylmagnesium bromide in diethyl ether was prepared by dissolving 15.5 g of 3M methylmagnesium bromide solution (in diethyl ether) in 100 ml of specially dried diethyl ether. While stirring at 25°-30° , a solution of 25.8 g of 1,3-bis(2-tetrahydropyranyloxy)-2-propanone, prepared as above, in 100 ml of diethyl ether was added dropwise. A white solid separated and refluxing occurred. The mixture was warmed to maintain reflux for 1 hour, then allowed to stand for 16 hours. Saturated ammonium chloride solution (100 ml) was added very slowly and when addition was completed, the layers were separated. The aqueous layer was extracted (2 × 100 ml) with diethyl ether. The ether solutions were combined, washed (2 × 100 ml) with water and dried over magnesium sulfate. The dried solution was concentrated and distilled to give 16.2 g of 2-methyl-1,3-bis(2-tetrahydropyranyloxy)-2-propanol, b.p. 121°-136°/2--3 × 10- 4 mm. was added dropwise A white solid separated refluxing The mixture was warmed to maintain reflux for 1 hour Saturated ammonium chloride solution (100 ml) was added very slowly when addition the layers were separated The aqueous layer was extracted (2 × 100 ml) with diethyl ether washed (2 × 100 ml) with water dried over magnesium sulfate The dried solution was concentrated distilled

Conditions: temp:85.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 236.3 g 3,4-dihydropyran and 90.1 g 1,3-dihydroxy-2-propanone, to which had been added 20 drops of concentrated hydrochloric acid, was heated to 85° C at which temperature, an exothermic reaction began. A cooling bath was applied to maintain the temperature in the range 85°-95° C during the next 15 minutes when heat was again applied to maintain the temperature at 85°-95° C for 2 hours. Excess dihydropyran was removed by warming under reduced pressure and the residue was dissolved in 600 ml of diethyl ether. The ether solution was washed (4 × 200 ml) with 5% aqueous sodium carbonate, then with water (3 × 300 ml) and dried over magnesium sulfate. The dried solution was distilled under reduced pressure to give 172.7 g of 1,3-bis(2-tetrahydropyranyloxy)-2-propanone, b.p. 90°-97°/2 × 10-4 mm. an exothermic reaction A cooling bath was applied to maintain the temperature in the range 85°-95° C during the next 15 minutes when heat to maintain the temperature at 85°-95° C for 2 hours Excess dihydropyran was removed by warming under reduced pressure the residue was dissolved in 600 ml of diethyl ether The ether solution was washed (4 × 200 ml) with 5% aqueous sodium carbonate with water (3 × 300 ml) and dried over magnesium sulfate The dried solution was distilled under reduced pressure

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

Procedure: 9.0 g of dihydroxyacetone dimer, 21.0 g of 3,4-dihydro-2H-pyran and a catalytic amount of p-toluenesulfonic acid were added to 70 ml of dichloromethane and stirred under ice-cooling for 3 hours. After the completion of the reaction, 150 ml of diethyl ether was added thereto. The mixture was then washed with a saturated aqueous solution of sodium hydrogencarbonate and dried over anhydrous magnesium sulfate. After distilling off the solvent, the oily residue thus obtained was subjected to chromatography wherein silica gel was employed as a carrier while hexane/ethyl acetate was employed as a mobile phase. Thus 16.5 g of 1,3-bis(2-tetrahydro-pyranyloxy)propan-2-one was obtained as a colorless viscous liquid. cooling for 3 hours was added The mixture was then washed with a saturated aqueous solution of sodium hydrogencarbonate dried over anhydrous magnesium sulfate After distilling off the solvent the oily residue thus obtained