The selective formation of the heterocyclic salt ((1,4-dioxane-2,5-diyl)-bis-(methylene))-bis-(triphenylphosphonium) chloride was observed when epichlorohydrin and triphenylphosphine were reacted in CH2Cl2 at room temperature. Slow evaporation from a mixture of ethanol and ethyl acetate allows to isolate monocrystals of the heterocyclic phosphonium salt. Mechanistic investigations point to the formation of the zwitterionic intermediate 1-chloro-3-(triphenylphosphonio)-propan-2-olate, which can dimerize and generate the 1,4-dioxane derivative. In the exclusive presence of a Brønsted acid as HCl, which usually facilitates epoxide ring opening, the exclusive formation of 1,3-dichloro-2-propanol was although observed. Also, when epichlorohydrin, PPh3, and a stoichiometric amount of HCl were mixed, (2-chloro-3-hydroxypropyl)-triphenylphosphonium chloride was formed and its isolation in pure form provides monocrystals subjectable to X-ray analysis.

Unconventional reactivity of epichlorohydrin in the presence of triphenylphosphine: isolation of ((1,4-dioxane-2,5-diyl)-bis-(methylene))-bis-(triphenylphosphonium) chloride

Mannu A.;Di Pietro M. E.;Sacchetti A.;Mele A.
2021-01-01

Abstract

The selective formation of the heterocyclic salt ((1,4-dioxane-2,5-diyl)-bis-(methylene))-bis-(triphenylphosphonium) chloride was observed when epichlorohydrin and triphenylphosphine were reacted in CH2Cl2 at room temperature. Slow evaporation from a mixture of ethanol and ethyl acetate allows to isolate monocrystals of the heterocyclic phosphonium salt. Mechanistic investigations point to the formation of the zwitterionic intermediate 1-chloro-3-(triphenylphosphonio)-propan-2-olate, which can dimerize and generate the 1,4-dioxane derivative. In the exclusive presence of a Brønsted acid as HCl, which usually facilitates epoxide ring opening, the exclusive formation of 1,3-dichloro-2-propanol was although observed. Also, when epichlorohydrin, PPh3, and a stoichiometric amount of HCl were mixed, (2-chloro-3-hydroxypropyl)-triphenylphosphonium chloride was formed and its isolation in pure form provides monocrystals subjectable to X-ray analysis.
2021
Dioxane
Epichlorohydrin
Phosphonium
Triphenylphosphine
Zwitterion
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1166454
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