title: Stereospecific consecutive epoxide ring expansion with dimethylsulfoxonium methylide.
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.
authors: Department of Organic Chemistry, Kiev Polytechnic Institute, pr. Pobedy 37, 03056 Kiev, Ukraine.
authors: Ekaterina D
authors: ED
authors: Butova
authors: Anastasiya V
authors: AV
authors: Barabash
authors: Anna A
authors: AA
authors: Petrova
authors: Christian M
authors: CM
authors: Kleiner
authors: Peter R
authors: PR
authors: Schreiner
authors: Andrey A
authors: AA
authors: Fokin
mesh_terms: D004852:Epoxy Compounds / Q000737:chemistry*; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D013237:Stereoisomerism; D013452:Sulfonium Compounds / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D004852:Epoxy Compounds; D013452:Sulfonium Compounds; C554865:dimethylsulfoxonium methylide