Reaction of dialkyl carbonates with alcohols: Defining a scale of the best leaving and entering groups

Tundo, Pietro; Aricò, Fabio; Rosamilia, Anthony E.; Rigo, Maurizio; Maranzana, Andrea; Tonachini, Glauco

doi:10.1351/PAC-CON-08-12-02

Pure Appl. Chem., 2009, Vol. 81, No. 11, pp. 1971-1979

http://dx.doi.org/10.1351/PAC-CON-08-12-02

Published online 2009-10-30

Reaction of dialkyl carbonates with alcohols: Defining a scale of the best leaving and entering groups

Pietro Tundo^1,2*, Fabio Aricò^1,2, Anthony E. Rosamilia², Maurizio Rigo², Andrea Maranzana^3,2 and Glauco Tonachini³

¹ Department of Environmental Sciences, Ca’ Foscari University of Venice, Dorsoduro 2137-30123, Venice, Italy
² Interuniversity Consortium “Chemistry for the Environment”, Via delle Industrie, 21/8 30175 Marghera, Venice, Italy
³ Department of General Chemistry and Organic Chemistry, University of Torino, Corso Massimo D’Azeglio 48, I-10125 Torino, Italy

Abstract: A series of dialkyl and methyl alkyl carbonates has been synthesized and their reactivity investigated. The behavior of preferential leaving and entering groups for the newly synthesized carbonates has been accurately investigated. Both experimental and computational studies agreed that the scale of leaving groups follows the trend: PhCH₂O^–, MeO^– ≥ EtO^–, CH₃(CH₂)₂O^–, CH₃(CH₂)₇O^– > (CH₃)₂CHO^– > (CH₃)₃CO^–. Accordingly, the scale of the entering group has the same trend, with t-butoxide being the worst entering group. A preliminary attempt to rationalize the nucleofugality trends, limited to the (CH₃)₃CO^– and CH₃O^– groups, has indicated that a likely origin of the observed trends lies in the different entropic contributions and solvation effects.