Issue 32, 2012

Carbonate, acetate and phenolate phosphonium salts as catalysts in transesterification reactions for the synthesis of non-symmetric dialkyl carbonates

Abstract

Methyl trioctylphosphonium methyl carbonate [P8881]+[MeOCO2] was prepared by the alkylation of trioctyl phosphine with the non-toxic dimethyl carbonate. This salt was a convenient source to synthesize different ionic liquids where the methyl trioctylphosphonium cation was coupled to weakly basic anions such as bicarbonate, acetate, and phenolate. At 90–220 °C, all these compounds [P8881]+X; X = MeOCO2; HOCO2; AcO; PhO were excellent organocatalysts for the transesterification of dimethyl and diethyl carbonate with primary and secondary alcohols, including benzyl alcohol, cyclopentanol, cyclohexanol, and the rather sterically hindered menthol. Conditions were optimized to operate with very low catalyst loadings up to 1 mol% and to obtain non-symmetric dialkyl carbonates (ROCO2R′; R = Me, Et) with selectivity up to 99% and isolated yields >90%. The catalytic performance of the investigated ionic liquids was discussed through a cooperative mechanism of simultaneous activation of both electrophilic and nucleophilic reactants.

Graphical abstract: Carbonate, acetate and phenolate phosphonium salts as catalysts in transesterification reactions for the synthesis of non-symmetric dialkyl carbonates

Supplementary files

Article information

Article type
Paper
Submitted
29 Feb 2012
Accepted
14 Jun 2012
First published
14 Jun 2012

Org. Biomol. Chem., 2012,10, 6569-6578

Carbonate, acetate and phenolate phosphonium salts as catalysts in transesterification reactions for the synthesis of non-symmetric dialkyl carbonates

M. Selva, M. Noè, A. Perosa and M. Gottardo, Org. Biomol. Chem., 2012, 10, 6569 DOI: 10.1039/C2OB25447F

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