Hydroxycarboxylic acid amide lactones

When /8-propiolactone is heated under pressure with anhydrous ammonia, /3-hydroxypropionamide is obtained. A mole of /3-propiolactone (72 g) is heated under pressure with 5.87 moles (100 g) of ammonia for 16 hr at 100 C to obtain a 50 per cent yield of crude /3-hydrox5rpropionamide, which can be purified by vacuum distillation. By a dehydration reaction, the amination of the lactone of a y-hydroxycarboxylic acid yields a stable cyclic amide or lactam, as is the case when y-butyrolactone is converted to a-pyrrolidone. However, owing to the instability of the four-membered ring, a lactam cannot be formed from ammonia and the lactone of a /8-hydroxycarboxylic acid, such as -propiolactone. When hydroxy-propionamide is dehydrated, no lactam is formed. Only unsaturated acid derivatives can be obtained, as shown in the equation below. 

Generally, lactones with five-membered and six-membered rings are not too reactive. They are relatively stable in acidic solutions, where they typically arise by spontaneous dehydration of hydrox-ycarboxylic adds. In aqueous solutions, particularly in alkaline solutions, the lactone ring opens with the formation of a salt of the hydroxycarboxylic acid. The original lactone may result after acidification, especially on heating. Lactones react with alcohols to form esters and, similarly, the lactone ring opens on reaction with amino compounds to form amides. 

A mixture of phenylacetic acid, benzyl alcohol, and tri-n-butylamine in methylene chloride added under argon to a mixture of l-methyl-2-bromopyridinium iodide and methylene chloride, and refluxed 3 hrs. benzyl phenylacetate. Y 97%. F. e., also with l-methyl-2-chloropyridinium iodide, s. T. Mukaiyama et al., Chem. Lett. 1975, 1045 Bull. Chem. Soc. Japan 50, 1863 (1977) carboxylic acid amides from amines (cf. Synth. Meth. 26, 367) s. ibid. 1975, 1163 3,4-dihydro-2H-pyrido-[1,2-a]pyrimid-2-one as acid scavenger cf. ibid. 1976, 13, 57 lactones from hydroxycarboxylic acids (cf. Synth. Meth. 17, 320) with 2-chloropyridine methio-dide and triethylamine s. ibid. 1976, 49 esters with 2 halogeno-3-ethylbenzothia-zolium salts of ibid. 1976, 267 2-chloro-N-methylbenzothiazolium triflate as condensing agent s. F. Souto-Bachiller, G. S. Bates, and S. Masamune, Chem. Com-mun. 1976, 719. 

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