This synthetic process of (CAS NO. ) needs a flask. A 500-mL, three-necked, round-bottomed flask is equipped with a mechanical stirrer, a short gas inlet tube, and an efficient reflux condenser fitted with a potassium hydroxide drying tube. The flask is charged with 13.4 g (0.05 mol) of 3-benzyl-5-(2-hydroxyethyl)-4-methyl-1,3-thiazolium chloride, 72.1 g (1.0 mol) of butyraldehyde, 30.3 g (0.3 mol) of triethylamine, and 300 mL of absolute ethanol. A slow stream of nitrogen is begun, and the mixture is stirred and heated in an oil bath at 80 °C. After 1.5 hr the reaction mixture is cooled to room temperature and concentrated by rotary evaporation. The residual yellow liquid is poured into 500 mL of water contained in a separatory funnel, and the flask is rinsed with 150 mL of dichloromethane which is then used to extract the aqueous mixture. The aqueous layer is extracted with a second 150 mL portion of dichloromethane. The combined organic phases are washed with 300 mL of saturated sodium bicarbonate and with 300 mL of water. The dichloromethane is removed by rotary evaporation under slightly diminished pressure. Distillation through a 20 cm Vigreux column gives 51–54 g (71–74%) of 5-Hydroxy-4-octanone as a colorless to light-yellow liquid.

The synthetic route of 5-Hydroxy-4-octanone is as follows:

This procedure is representative of a new general method for the preparation of noncyclic acyloins by thiazolium-catalyzed dimerization of aldehydes in the presence of weak bases. The advantages of this method over the classical reductive coupling of esters or the modern variation, in which the intermediate enediolate is trapped by silylation are the simplicity of the procedure, the inexpensive materials used, and the purity of the products obtained.