Fluorinated alcohols enable olefin epoxidation by H2O2: template catalysis.
Experimental observations show that direct olefin epoxidation by H(2)O(2), which is extremely sluggish otherwise, occurs in fluorinated alcohol (R(f)OH) solutions under mild conditions requiring no additional catalysts. Theoretical calculations of ethene and propene epoxidation by H(2)O(2) in the gas phase and in the presence of methanol and of two fluorinated alcohols, presented in this paper, show that the fluoro alcohol itself acts as a catalyst for the reaction by providing a template that stabilizes specifically the transition state (TS) of the reaction. Thus, much like an enzyme, the fluoro alcohol provides a complementary charge template that leads to the reduction of the barrier by 5-8 kcal mol(-)(1). Additionally, the fluoro alcohol template keeps the departing OH and hydroxyalkenyl moieties in close proximity and, by polarizing them, facilitates the hydrogen migration from the latter to form water and the epoxide product. The reduced activation energy and structural confinement of the TS over the fluoro alcohol template render the epoxidation reaction observable under mild synthetic conditions.
de Visser
Samuël P
SP
Department of Organic Chemistry and The Lise Meitner-Minerva Center for Computational Quantum Chemistry, Hebrew University, Givat Ram Campus, 91904 Jerusalem, Israel.
Kaneti
Jose
J
Neumann
Ronny
R
Shaik
Sason
S