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

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)(2)O-, CH3(CH2)(7)O- > (CH3)(2)CHO- > (CH3)(3)CO-. 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)(3)CO- and CH3O- groups, has indicated that a likely origin of the observed trends lies in the different entropic contributions and solvation effects.