THE ACETOLYSIS OF SOME HYDROXYTETRAHYDRO-2-PYRANS

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Abstract
The reaction between acetic anhydride and several hydroxytetrahydropyrans in the presence of boron trifluoride has been studied. 2-Methyl-3-hydroxytetrahydropyran, 2-hydroxymethyl-4,5-dihydroxytetrahydropyran, and 3,4-dihydroxytetrahydropyran all underwent normal acetolysis to the expected straight-chain polyol acetates. Optically active forms of cis-and trans-3,4-dihydroxytetrahydropyran gave the same, inactive pentanetetrol, showing that racemization of the active centers had accompanied ring cleavage. 2-Hydroxymethyl-tetrahydropyran gave 1,3,6-hexanetriol besides the expected 1,2,6-isomer. The reagent did not cleave 4-hydroxytetrahydropyran nor dihydro-D-galactal, but the latter underwent hydroxyl inversion to give dihydro-D-altral. 1,5-Anhydro-D-sorbitol (polygalitol) appeared to undergo both ring fission and inversion.