Unusual transformations of monopropargyl esters 2,3- and 1,3-butanediols

Esters occupy a special place in the field of chemistry of oxygen-containing acetylene derivatives due to the presence of highly reactive centers. Acetylene esters of glycols under acid-catalytic hydration conditions usually form ketoxyesters. The article set the task of finding ways to synthesize previously unknown mono- and dipropargyl esters of glycols, as well as to study their synthetic potential and practical use. The results of a study of acid-catalytic intramolecular cyclohydration and synthesis of heterocyclic compounds based on propargyl esters of glycols are presented. The latter were monopropargyl esters of 2,3- and 1,3-butanediols (I, II), which were obtained by condensation of propargyl alcohol with the corresponding glycols. Monopropargyl esters of 2,3-butanediol (I) was subjected to unusual transformations under the conditions of the hydration reaction. It was found that the monopropargyl ether of 2,3-butanediol (I), when heated in a vacuum with KOH, turns not into an individual product, but into a mixture of 4,5-dimethyl-2-vinyl-1,3-dioxolan (IV) and 3,5,6-trimethyl-1,4-dioxene (V). In an individual form, vinyl substituted 1,3-dioxane (VI) was obtained by counter synthesis by condensation of 1,3-butanediol with acrolene. Using the propensity of propargyl compounds to change in the basic medium, the possibility of converting monopropargyl esters of 2,3- and 1,3-butanediols (I, II) into oxygen-containing heterocycles was studied. The structure of the obtained heterocyclic compounds is confirmed by PMR and IR absorption spectra.