Propanal → 3-Hydroxy-2-(1-hydroxypropyl)-6-methyl-4H-pyran-4-one

Allomaltol (12.6 g, 100 mmol, 1 eq.) was added to 100 ml water and the pH of the solution was adjusted to 10.5 using 50% aqueous sodium hydroxides. Propionaldehyde (8.7 g, 150mmol, 1.5 eq.) dissolved in 50 ml methanol was slowly added dropwise over 1 hour and the solution allowed to stir at room temperature for 48 hours. After adjustment to pH 1 with 37% hydrochloric acid, the reaction mixture was evaporated to dryness and the residue taken up into 300 ml of dichloromethane. The organic layer was washed with water (150 ml), dried over anhydrous sodium sulphate, filtered and concentrated to yield the crude product. Recrystallisation from toluene afforded the pure product (14.5 g, 78.9%) as a white crystalline solid. m.p. 134-136° C. [lit. 132-135° C. Ellis (1993)].

1. additionwas slowly added dropwise over 1 hour
2. customAfter adjustment to pH 1 with 37% hydrochloric acid, the reaction mixture was evaporated to dryness
3. washThe organic layer was washed with water (150 ml)
4. dry with materialdried over anhydrous sodium sulphate
5. filtrationfiltered
6. concentrationconcentrated
7. customto yield the crude product
8. customRecrystallisation from toluene

ORD record

ord-bf3fa72bd9c74086a4a7d7a1cae75dc6

Source dataset

uspto-grants-2002_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06448273B1