Phosphoric Acid → 12-Methyl-9-oxa-14-tetradecanolide

Participants

Reaction Conditions

Reaction Steps

A solution of 30 g (520 mmol) of 95 percent sodium methylate in 220 ml of dry methanol was heated to reflux. Thereupon, 60 ml (520 mmol) of dimethyl malonate were allowed to drop in, the reaction mixture was heated under reflux for a further 15 min. and then 182 g of 66 percent 12-bromo-3-methyl-6-oxadodecan-1-ol from the preceding batch were added thereto. After heating under reflux for 14 hours the reaction mixture was added to 1.6 l of water/tert-butyl methyl ether (1:1) and made acid with concentrated phosphoric acid. The organic phase was separated and the aqueous phase was extracted twice with 500 ml of tert-butyl methyl ether each time. The combined organic phases were dried over magnesium sulphate, concentrated to dryness on a rotary evaporator, taken up in 400 ml of methanol and treated with 99 g (1.5 mol) of 85 percent potassium hydroxide. Methanol and byproducts were distilled off at 180° C./20-23mbar during 1 h. Thereupon, the reaction mixture was treated with 200 ml (2.4 mol) of 3-chloro-1,2-propanediol and heated to 140° C. for 1 h. After distilling off the excess 3-chloro-1,2-propanediol the reaction vessel was fitted with a condenser and separator and treated with 6.0 g (86 mmol) of potassium methylate in 450 ml of anhydrous glycerol. After stirring at 140° C./20-30 mbar for 15 minutes the mixture was heated to reflux at 155° C./4-6 mbar for 3 days under the separator, with 6.0 g (86 mmol) of potassium methylate being added every 24 hours. The separated glycerol was poured into 800 ml of water and extracted three times with 500 ml of tert-butyl methyl ether each time. After drying the combined organic extracts over magnesium sulphate, concentration on a rotary evaporator and distillation at 95-97° C./0.04 mbar there were obtained 59 g (52%) of 12-methyl-9-oxa-14-tetradecanolide (1) as a colorless liquid with the following characteristics.

Provenance & Evidence