RESUMO
New density functional theory (DFT) computations are reported concerning the mechanism of the Suzuki-Miyaura cross-coupling reaction of aryl halides and aryl boronic acids catalyzed by palladium phosphine complexes. The calculations are aimed at refining the understanding of the overall catalytic mechanism using state of the art theoretical approaches (including, for the first time, an attempt to describe the Gibbs energy of the reactant base in a realistic way). New experimental results (Thomas and Denmark, Science, 2016, 352, 329-332) concerning pre-transmetallation intermediates with a Pd-O-B linkage provide an invaluable benchmark to test the accuracy of the calculations. The calculations show that bottlenecks to catalysis associated with oxidative addition, X-to-O substitution at Pd, and transmetallation can lie close in energy.
RESUMO
Novel density functional theory calculations are presented regarding a mechanism for prebiotic amino acid synthesis from alpha-keto acids that was suggested to happen via catalysis by dinucleotide species. Our results were analysed with comparison to the original hypothesis (Copley et al., PNAS, 2005, 102, 4442-4447). It was shown that the keto acid-dinucleotide hypothesis for possible prebiotic amino acid synthesis was plausible based on an initial computational analysis, and details of the structures for the intermediates and transition states showed that there was wide scope for interactions between the keto acid and dinucleotide moieties that could affect the free energy profiles and lead to the required proto-metabolic selectivity.