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Guanidine–Guanidinium Cooperation in Bifunctional Artificial Phosphodiesterases Based on Diphenylmethane Spacers; gem-Dialkyl Effect on Catalytic Efficiency

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journal contribution
posted on 19.02.2016, 03:11 by Riccardo Salvio, Luigi Mandolini, Claudia Savelli
Diphenylmethane derivatives 13, decorated with two guanidine units, are effective catalysts of HPNP transesterification. Substitution of the methylene group of the parent diphenylmethane spacer with cyclohexylidene and adamantylidene moieties enhances catalytic efficency, with gem-dialkyl effect accelerations of 4.5 and 9.1, respectively. Activation parameters and DFT calculations of the rotational barriers around the C–Ar bonds indicate that a major contribution to the driving force for enhanced catalysis is entropic in nature.