Sodium Hydroxide → 2H-Pyran-2-one, tetrahydro-5-pentyl-

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Reaction Conditions

Reaction Steps

1560.0 g of ethanol and 663.0 g (max. 2.74 mol) of 82.7% methyl 4-formylnonanoate obtained in Example 1 are placed in a four-liter round-bottomed flask with a mechanical stirrer and a thermometer, and the mixture is cooled to 0° C. 41.6 g (1.10 mol) of sodium borohydride are then added dropwise over four hours, without exceeding 5° C. in the bulk. Stirring is continued after the end of the addition for a further 24 hours at 0° C. 1900.0 g of aqueous 10% sodium hydroxide solution are added dropwise over two hours, without exceeding 10° C. in the bulk. A white precipitate forms. Stirring is continued until the dissolution of the precipitate is complete (about two hours). The flask is placed under a vacuum of about 3990 Pa and the ethanol is distilled off. The aqueous phase obtained is extracted twice with 200 ml of a mixture of toluene and hexane (50/50) to remove the neutral products. The aqueous phase is then cooled to 0° C. The resulting phase is acidified with 1900.0 g of 10% hydrochloric acid for three hours, without exceeding 10° C. in the bulk. After the end of the addition, stirring is continued for four hours, while allowing the temperature of the reaction medium to rise to room temperature (20° C.). The phases are allowed to separate by settling and the organic phase is recovered. The aqueous phase is extracted twice with 200 ml of toluene. The organic phases are combined and are washed twice with 100 ml of water and once with 200 ml of brine, and then concentrated under reduced pressure (3990 Pa). 696.0 g of a crude product are obtained, and are then blanched at 133 Pa to give 468.0 g of 86.1% 5-pentyltetrahydropyran-2-one. After distillation on a Vigreux column, a core fraction of 289.0 g (1.70 mol) of 98.3% 5-pentyltetrahydropyran-2-one is obtained (90-2° C./27 Pa) in a yield of 61%.

Provenance & Evidence