Stereospecific Consecutive Epoxide Ring Expansion With Dimethylsulfoxonium Methylide

J Org Chem. 2010 Sep 17;75(18):6229-35. doi: 10.1021/jo101330p.

Abstract

Consecutive ring-expansion reactions of oxiranes with dimethylsulfxonium methylide were studied experimentally and modeled computationally at the density functional theory (DFT) and second-order Møller-Plesset (MP2) levels of theory utilizing a polarizable continuum model (PCM) to account for solvent effects. While the epoxide to oxetane ring expansion requires 13-17 kcal mol(-1) activation and occurs at elevated temperatures, the barriers for the ring expansions to oxolanes are higher (ca. 25 kcal mol(-1)) and require heating to 125 °C. Further expansions of these oxolanes to the six-membered oxanes are hampered by high barriers (ca. 40 kcal mol(-1)). We observe the complete conservation of the enantiomeric purities for the nucleophilic ring expansions of enantiomeric 2-mono- and 2,2-disubstituted epoxides and oxetanes with dimethylsulfoxonium methylide. This is a convenient general approach for the high-yielding preparation of optically active four- and five-membered cyclic ethers from oxiranes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Epoxy Compounds / chemistry*
  • Molecular Conformation
  • Molecular Dynamics Simulation
  • Stereoisomerism
  • Sulfonium Compounds / chemistry*
  • Thermodynamics

Substances

  • Epoxy Compounds
  • Sulfonium Compounds
  • dimethylsulfoxonium methylide