The effect of electrostatic interactions on conformational equilibria of multiply substituted tetrahydropyran oxocarbenium ions

Michael T. Yang, K. A. Woerpel

Research output: Contribution to journalArticlepeer-review

Abstract

The three-dimensional structures of dioxocarbenium ions related to glycosyl cations were determined by an analysis of spectroscopic, computational, and reactivity data. Hypothetical low-energy structures of the dioxocarbenium ions were correlated with both experimentally determined 1H NMR coupling constants and diastereoselectivity results from nucleophilic substitution reactions. This method confirmed the pseudoaxial preference of C-3 alkoxy-substituted systems and revealed the conformational preference of the C-5 alkoxymethyl group. Although the monosubstituted C-5 alkoxymethyl substituent preferred a pseudoequatorial orientation, the C-5-C-6 bond rotation was controlled by an electrostatic effect. The preferred diaxial conformer of the trans-4, 5-disubstituted tetrahydropyranyl system underscored the importance of electrostatic effects in dictating conformational equilibria. In the 2-deoxymannose system, although steric effects influenced the orientation of the C-5 alkoxymethyl substituent, the all-axial conformer was favored because of electrostatic stabilization.

Original languageEnglish (US)
Pages (from-to)545-553
Number of pages9
JournalJournal of Organic Chemistry
Volume74
Issue number2
DOIs
StatePublished - Jan 16 2009

ASJC Scopus subject areas

  • Organic Chemistry

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