Preparation of ethyl 3-hydroxy-2,3-dimethylbutanoate
60 g of zinc are freed fom oxide and oil by washing successively with warm sodium hydroxide solution, then dilute acid, water and alcohol. After being dried in an air oven, an small quantity is added to a mixtere of 90 g pure dry acetone and 182 g of ethyl 2-bromopropanoate contained in a large flask provided with a reflux condenser. The flask is gradually warmed on a water bath until a reaction commences, and if it proceeds too vigorously, cooling must be applied. More zinc is added from time to time as the reaction subsides until some of the metal remain undisolved (about 45 g metallic zinc are usually required), and after the final addition, heating is contued for 23 hours. The supy liquid is poured off from the attacked metal, and water added. The basic zinc bromide which is precipitated is disolved by the addition of a sufficient quantity of dute sulphuric acid, and the oily layer is extracted with ether and separated. The extract is washed three times with dulute sulphuric acid, then with water, and dried over calcium chloride. After the ether is removed, the residue is distilled at 30 mmHg, when the pure ester passes over about 105° C. Yield 50%; colourless oil, insoluble in water; b.p. 105° C/30 mmHg.
Systematic organic chemistry, by W. M. Cumming, 134-135, 1937.
ethyl 3-hydroxy-2,3-dimethylbutanoate, MolPort-020-166-748, NE21967, EN300-78341