… when they are almost finished!
Enjoy the last days 😉
We have just published very interesting studies about the Henry reaction, which allow understanding more in detail the activation of the substrates by a very effective squaramide. Enjoy them…
Abstract. This computational and experimental study represents the first case where “push-pull π+/π-” (PPππ) systems have shown a concrete application in Chemistry apart from in spectral tuning. The most notable finding of this investigation was that a mode of interaction unprecedented in catalysis, a PPππ system, played a crucial role in the Henry reaction catalyzed by a NOBIN-based squaramide. The results show that the PPππ system stabilizes the most favorable pathway, P1, with 2.7-4.7 kcal/mol. This is vital for the differentiation in energy of P1 over the rest of the pathways and directly affects both the reactivity and stereoselectivity of this reaction. These results suggest that PPππ systems are promising tools with great potential for catalysis.
Optimizing Accuracy and Computational Cost in Theoretical Squaramide Catalysis: the Henry Reaction, Alegre Requena J. V.; Marqués-López, E.; Herrera, R. P. Chem. Eur. J. 2017, DOI: 10.1002/chem.201702841.
Abstract. This study represents the first example where the accuracy of different combinations of density functional theory (DFT) methods and basis sets has been compared in squaramide catalysis. After an optimization process of the precision obtained and the computational time required in the computational calculations, highly precise results were achieved compared to the experimental outcomes while using the least amount of time as possible. Here, we have explored computationally and experimentally the mechanism of squaramide-catalyzed Henry reaction. This is a complex reaction of about 100 atoms and a great number of diverse non-covalent interactions. Moreover, this research is one of the scarce examples where the organocatalyst acts in a trifunctional manner and is the first investigation in which a trifunctional squaramide catalyst has been employed. Functional ωB97X-D showed the best results when used with different versions of the 6-311 basis sets, leading to highly accurate calculations of the outcomes of the Henry reaction using nine aldehydes with different structural characteristics. Furthermore, in these relatively large systems, the use of a split-valence triple-zeta basis set saves a large amount of time compared to using larger basis sets that are sometimes employed in organocatalytic studies, such as the TZV and Def2TZV basis set families.
Roberto will be with us this summer working in the lab before leaving for an Erasmus academic stay in September.
Asymmetric Organocatalytic Synthesis of Substituted Chiral 1,4-Dihydropyridine Derivatives. Fernando Auria-Luna, Eugenia Marqués-López, M. Concepción Gimeno, Roghayeh Heiran, Somayeh Mohammadi, and Raquel P. Herrera, J. Org. Chem. 2017, 82, 5516–5523.
Abstract. The first cinchona-alkaloid-organocatalyzed enantioselective synthesis of chiral 1,4-dihydropyridine derivatives is described. Bis-cinchona catalyst 3b activates the Michael addition reaction between malononitrile derivatives 2 and enamines 1, affording the appealing and highly substituted 1,4-dihydropyridines 4 with very good results in most cases. This is one of very few examples of the synthesis of chiral 1,4-dihydropyridines by an enantioselective catalytic procedure. The highly substituted final compounds are of interest for their potential biological activity. This efficient protocol opens the door to a new area of research for the asymmetric construction of these skeletons for which enantioselective syntheses are still very limited.
Our collaborator, Concepción Gimeno, awardee of the “IUPAC 2017 Distinguished Women in Chemistry or Chemical Engineering”
Last week, we celebrated Isaac’s birthday with a delicious cake that Sandra cooked for us.