Designing bifunctional alkene isomerization catalysts using predictive modelling

Controlling the isomerization of alkenes is important for the manufacturing of fuel additives, fine-chemicals and pharmaceuticals. But even if isomerization seems to be a simple unimolecular process, the factors that govern catalyst performance are far from clear. Here we present a set of models that describe selectivity and activity, enabling the rational design and synthesis of alkene isomerization catalysts. The models are based on simple molecular descriptors, with a low computational cost, and are tested and validated on a set of eleven known Ru-imidazol-phosphine complexes and two new ones. Despite their simplicity, these models show good predictive power, with R2 values of 0.60–0.85. Using a combination of principal components analysis (PCA) and partial least squares (PLS) regression, we construct a “catalyst map”, that captures trends in reactivity and selectivity as a function of electrostatic charge on the N* atom, EHOMO, polar surface area and the optimal mass substituents on P/distance Ru–P ratio. In addition to indicating “good regions” in the catalyst space, these models also give insight into mechanistic steps. For example, we find that the electrostatic charge on N*, EHOMO and polar surface area are crucial in the rate-limiting step, whereas the optimal mass of substituents on P/distance Ru–P is correlated with the product selectivity

Nitazoxanide in the treatment of Ascaris lumbricoides in a rural zone of Colima, Mexico

Functionalized carbene ligands: Increasing the steric bulk of R1 on 1 from H to tBu results in lengthening of the M-N bond (by up to 9 %), lowered activation energy for chelate opening (cf. 2) by 17 kcal mol -1, and improved binding of an amine and intramolecular hydrogen bonding (3). Iridium species with R1=tBu are effective catalysts of base-free intramolecular hydroamination, unlike less-hindered analogues. Copyright " 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.",,,,,,"10.1002/chem.201100521",,,"http://hdl.handle.net/20.500.12104/41220","http://www.scopus.com/inward/record.url?eid=2-s2.0-79957957253&partnerID=40&md5=e5f420da903f48ac5c6ea8173f95b40d",,,,,,"24",,"Chemistry - A European Journal",,"660