Unprecedented Multicomponent Organocatalytic Synthesis of Propargylic Esters via CO2 Activation
Fecha
2019-02-19Autor
Papastavrou, Argyro T.
Pauze, Martin Paule
Gómez Bengoa, Enrique
Vougioukalakis, Georgios C
Metadatos
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ChemCatChem 11(21) : 5379-5386 (2019)
Resumen
An efficient and straightforward organocatalytic method for the
direct, multicomponent carboxylation of terminal alkynes with
CO2 and organochlorides, towards propargylic esters, is reported
for the first time. 1,3-Di-tert-butyl-1H-imidazol-3-ium
chloride, a simple, widely-available, stable, and cost-efficient Nheterocyclic
carbene (NHC) precursor salt was used as the (pre)
catalyst. A wide range of phenylacetylenes, bearing electronwithdrawing
or electron-donating substituents, react with allylchlorides,
benzyl chlorides, or 2-chloroacetates, providing the
corresponding propargylic esters in low to excellent yields. DFT
calculations on the mechanism of this transformation indicate
that the reaction is initiated with the formation of an NHCcarboxylate,
by addition of the carbene to a molecule of CO2.
Then, the nucleophilic addition of this species to the corresponding
chlorides has been computed to be the rate limiting
step of the process