The synthesis of furans from acetylenic epoxides and diols

Acetylenic αβ-epoxides react with dilute sulphuric acid and mercuric sulphate on heating to give furans in good yields; the reaction involves an internal hydration at a terminal acetylenic carbon atom. Under the influence of sulphuric acid alone, only small quantities of furans are formed; the major products are acetylenic diols. These have been shown to be probable intermediates in the formation of the furans. When the epoxides are treated with dilute sulphuric acid in the presence of ethanol, monoethers of acetylenic diols are formed. Acetylenic βγ-epoxides have also been shown to give furans in the mercuric sulphate-catalysed reaction with sulphuric acid.