Studies on the chemistry of diols and cyclic ethers-52. Mechanism and stereochemistry of dehydration of oxolanes to dienes

Árpád Molnár, Mihály Bartók

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

On γ-Al2O3, RPO4 and NaX zeolite, the dehydration of (±)-2,2,3,4,5,5-hexamethyloxolane (2) in the vapour phase leads to the formation of 2,3,4,5-tetramethyl-1,5-hexadiene (8) in a slow process, while meso-2,2,3,4,5,5-hexamethyloxolane (3) is converted to 2, 3,4,5-tetramethyl-2, 4-hexadiene (7) with high selectivity in a fast reaction. These differences in reaction rate and selectivity indicate that the dehydration of 2 takes place by an E2 mechanism. In contrast, the steric strain in 3 results in ring opening by an E1 mechanism. These conclusions are supported by the nonselective transformations of 2,2,5,5-tetramethyloxolane (1) and 2,2,6,6-tetramethyloxane (4), and the dehydration of 1, 2 and 3 in the presence of formic acid in the liquid phase. The experimental observation prove that both the reactivity and the reaction directions in the dehydration of stereoisomeric oxolanes are determined by steric factors.

Original languageEnglish
Pages (from-to)131-141
Number of pages11
JournalTetrahedron
Volume43
Issue number1
DOIs
Publication statusPublished - 1987

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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