Access to polysubstituted naphthalenes and anthracenes via a retro -Diels–Alder reaction

Boron-Locked Starazine - A Soluble and Fluorescent Analogue of Starphene

A starlike heterocyclic molecule containing an electron‐deficient nonaaza‐core structure and three peripheral isoquinolines locked by three tetracoordinate borons, namely isoquinoline‐nona‐starazine (QNSA), is synthesized by using readily available reactants through a rather straightforward approach. This new heteroatom‐rich QNSA possesses a quasi‐planar π‐backbone structure, and bears phenyl substituents on borons which protrude on both sides of the π‐backbones endowing it with good solubility in common organic solvents. Contrasting to its starphene analogue, QNSA shows intense fluorescence with a quantum yield (PLQY) of up to 62 % in dilute solution.

Synthesis and docking calculations of tetrafluoronaphthalene derivatives and their inhibition profiles against some metabolic enzymes

Syntheses of tetrahydroepoxy, O-allylic, O-prenylic, and O-propargylic tetrafluoronaphthalene derivatives, starting from 1-bromo-2,3,4,5,6-pentafluorobenzene, are reported here for the first time. The O-substituted tetrafluoronaphthalene derivatives were designed and also synthesized via a one-pot nucleophilic substitution reaction in excellent yields, whereas the tetrafluorotetrahydroepoxynaphthalene derivate was synthesized via a reduction reaction in excellent yield. The chemical structures of all the synthesized molecules were characterized by nuclear magnetic resonance, infrared spectroscopy, and high-resolution mass spectrometry techniques. In this study, a series of novel tetrafluoronaphthalene derivatives (2, 2a, 4-6) was tested toward several enzymes including α-glucosidase, acetylcholinesterase (AChE), and human carbonic anhydrase I and II (hCA I/II). The tetrafluoronaphthalene derivatives 2, 2a, and 4-6 showed IC₅₀ and K_i values in the range of 0.83-1.27 and 0.71-1.09 nM against hCA I, 1.26-1.85 and 1.45-5.31 nM against hCA II, 39.02-56.01 and 20.53-56.76 nM against AChE, and 15.27-34.12 and 22.58-30.45 nM against α-glucosidase, respectively. Molecular docking calculations were made to determine the biological activity values of the tetrafluoronaphthalene derivatives against the enzymes. After the calculations, ADME/T analysis was performed to examine the effects on human metabolism. Finally, these compounds had antidiabetic and anticholinesterase potentials.

Diels-Alder Reactivity of a Chiral Anthracene Template with Symmetrical and Unsymmetrical Dienophiles: A DFT Study

In this work, we used Density Functional Theory calculations to assess the factors that control the reactivity of a chiral anthracene template with three sets of dienophiles including maleic anhydrides, maleimides and acetoxy lactones in the context of Diels-Alder cycloadditions. The results obtained here (at the M06-2X/6-311++G(d,p) level of theory) suggest that the activation energies for maleic anhydrides and acetoxy lactones are dependent on the nature of the substituent in the dienophile. Among all studied substituents, only -CN reduces the energy barrier of the cycloaddition. For maleimides, the activation energies are independent of the heteroatom of the dienophile and the R group attached to it. The analysis of frontier molecular orbitals, charge transfer and the activation strain model (at the M06-2X/TZVP level based on M06-2X/6-311++G(d,p) geometries) suggest that the activation energies in maleic anhydrides are mainly controlled by the amount of charge transfer from the diene to the dienophile during cycloaddition. For maleimides, there is a dual control of interaction and strain energies on the activation energies, whereas for the acetoxy lactones the activation energies seem to be controlled by the degree of template distortion at the transition state. Finally, calculations show that considering a catalyst on the studied cycloadditions changes the reaction mechanism from concerted to stepwise and proceed with much lower activation energies.

How Alkali Cations Catalyze Aromatic Diels-Alder Reactions

We have quantum chemically studied alkali cation-catalyzed aromatic Diels-Alder reactions between benzene and acetylene forming barrelene using relativistic, dispersion-corrected density functional theory. The alkali cation-catalyzed aromatic Diels-Alder reactions are accelerated by up to 5 orders of magnitude relative to the uncatalyzed reaction and the reaction barrier increases along the series Li+ < Na+ < K+ < Rb+ < Cs+ < none. Our detailed activation strain and molecular-orbital bonding analyses reveal that the alkali cations lower the aromatic Diels-Alder reaction barrier by reducing the Pauli repulsion between the closed-shell filled orbitals of the dienophile and the aromatic diene. We argue that such Pauli mechanism behind Lewis-acid catalysis is a more general phenomenon. Also, our results may be of direct importance for a more complete understanding of the network of competing mechanisms towards the formation of polycyclic aromatic hydrocarbons (PAHs) in an astrochemical context.