title: Activation of Benzyl Aryl Carbonates: The Role of Cation-π Interactions.
abstract: Benzyl aryl carbonates can react with a nucleophile to yield an activated electrophile and an aryloxide anion. Previously, we had utilized this in the synthesis of α-nitro esters from nitroalkanes. To further understand the process of activation of these carbonates by nucleophiles, we have performed kinetic studies on the hydrolysis of carbonates using nucleophiles. Rate constants for the hydrolysis were obtained under pseudo-first-order conditions with DABCO as the nucleophile. A comparison of rate constant for hydrolysis of isobutyl phenyl carbonate with benzyl phenyl carbonate shows that the presence of benzyl group results in a 16-fold acceleration of hydrolysis rate. This indicates that the transition state for activation of carbonate is stabilized by cation-π interactions. A comparison of the rate constant for various aromatic rings indicates that electron-donating substituents on the benzyl groups accelerate the rate of hydrolysis. Studies were also carried out with DMAP as nucleophile and the results are presented. Our studies show that stable carbonates can be activated using nucleophiles. Activated acyl groups generated from acid anhydrides have been used in several enantioselective reactions. Our studies show that carbonates can be stable alternatives to acid anhydrides.
authors.affiliation: New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur P.O., Bangalore 560064, India.
authors.forename: Golipalli Ramana
authors.initials: GR
authors.lastname: Reddy
authors.affiliation: New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur P.O., Bangalore 560064, India.
authors.forename: Anusha S
authors.initials: AS
authors.lastname: Avadhani
authors.affiliation: International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur P.O., Bangalore 560064, India.
authors.forename: Sridhar
authors.initials: S
authors.lastname: Rajaram