p-Toluenesulfonic acid → 2-(Pyrid-3-yl)-1,3-oxathiane

Participants

Reaction Conditions

Reaction Steps

A solution of pyridine-3-carboxaldehyde (16 g), 3-mercaptopropan-1-ol (48 g) and para-toluenesulphonic acid (2.25 g) in 1,2-dichloroethane (1500 cc) is kept at the boil for 15 hours so that the water formed is removed by azeotropic distillation. After cooling to a temperature of about 20° C., the reaction mixture is washed three times with a 5 N aqueous solution of sodium hydroxide (750 cc in total) and then three times with distilled water (1500 cc in total). The organic phase is dried over anhydrous sodium sulphate and filtered, and the filtrate is concentrated to dryness under reduced pressure (20 mm Hg; 2.7 kPa) at 50° C. The product obtained (15.6 g) is chromatographed in neutral silica gel (200 g) contained in a column of diameter 3.7 cm. Elution is carried out successively with a cyclohexane/ethyl acetate mixture (80/20 by volume; 600 cc) and a cyclohexane/ethyl acetate mixture (70/30 by volume; 2700 cc), 300 cc fractions being collected. Fractions 5 to 11 are combined and concentrated to dryness under reduced pressure (20 mm Hg; 2.7 kPa) at 50° C. 2-(Pyrid-3-yl)-1,3-oxathiane (8.6 g) is thus obtained in the form of a yellow oil.

Provenance & Evidence