Naphthalene Framework Research Articles

Dual Excited State Proton Transfer Pathways in the Bifunctional Photoacid 6-Amino-2-naphtol.

This study investigates the photoacidity and excited state proton transfer (ESPT) pathways of a bifunctional molecule, 6-amino-2-naphthol (6N2OH), using absorption, steady-state fluorescence, time-resolved fluorescence, and theoretical calculations. 6N2OH attains four different prototropic forms in the excited state (cation, neutral, anion, or zwitterion) depending on pH of the solution. Interestingly, ESPT at the OH site of the molecule can be controlled by the protonation state of the amino substituent. Conversion of the electron donating NH2 group to the electron withdrawing NH3+ group brings about a reduction of more than 7 pKa units for the deprotonation of OH in the excited state. Further, the position of the NH2 substituent on the naphthalene framework is found to play an important role in dictating the ESPT pathways of aminonaphthols. Unlike most aminonaphthol derivatives that undergo ESPT only at the OH site, akin to substituted naphthols, 6N2OH undergoes ESPT at both OH and NH3+ sites, indicating its similarity to substituted naphthols and substituted naphthylamines. ESPT at the NH3+ site resulting in cation ↔ neutral equilibrium of 6N2OH in the excited state is well-corroborated by comparative studies with another reference photoacid, 6-amino-2-methoxynaphthalene (6N2M). Correlation of the acidity constants of 6N2OH with the σp parameters according to the Hammett model reveals that while 6N2OH can be treated either as naphthol or as naphthylamine in the ground state, the structure-function correlation cannot be extrapolated directly in the excited state, thus highlighting the rich and complex photophysics of bifunctional photoacids.

A Study of the Correlation between the Bulkiness of peri-Substituents and the Distortion of a Naphthalene Ring.

A systematic study on the distortion of a naphthalene ring was performed using steric repulsion between peri-substituents at the 1- and 8-positions. The introduction of bromo groups into the methyl groups of the 1,8-dimethylnaphthalene enhanced the steric repulsion to distort the naphthalene ring. X-ray crystallography revealed that 1,8-bis(bromomethyl)naphthalene had a vertical distortion with a 11.0° dihedral angle (α) between peri-substituents which disturbed the coplanarity of the naphthalene ring. On the other hand, the dihedral angle of 1,8-bis(dibromomethyl)naphthalene was smaller (α = 8.3°) despite the bulkier substituents. In this case, horizontal distortion of the naphthalene ring increased. These distortions should non-electronically activate the naphthalene framework. In order to evaluate their reactivity, nitration and hydrogenation were carried out; however, the 1,8-bis(dibromomethyl)naphthalene was intact under the employed conditions. A DFT calculation suggested that the inertness of the 1,8-bis(dibromomethyl)naphthalene is presumably due to the negative hyperconjugation of the (dibromo)methyl group.

Formation of a Naphthalene Framework by Rhodium(III)-Catalyzed Double C–H Functionalization of Arenes with Alkynes: Impact of a Supporting Ligand and an Acid Additive

AbstractAn efficient protocol has been developed for the synthesis of larger condensed arenes from aromatic hydrocarbons and internal alkynes. This protocol uses readily available [CpRhI2]n as a catalyst and Cu(OAc)2 as an oxidant and proceeds smoothly through undirected double C–H activation. The addition of trifluoroacetic acid has a crucial positive impact on the reaction selectivity and the yields of the target products. In contrast to the previously reported catalytic systems, the new conditions allow the use of both dialkyl- and diarylacetylenes with the same high efficiency.

Synthesis of novel benzohydrazide and benzoic acid derivatives: Crystal Structure, Hirshfeld surface analysis and DFT computational studies

New series of benzohydrazide/benzoic acid derivatives were synthesized (4a-b and 5a-b) and subjected to solid-state characterization by NMR spectroscopic measurements. The molecular and crystal structures of 4a and 5a have also been examined by single-crystal X-ray crystallography were reveal that naphthalene frameworks are close to planarity. Besides, the dihedral angle between the mean plane of the naphthalene ring system and the phenyl ring is 2.26(7) and 78.87(8)° for 4a and 5a, respectively. The molecules are linked through N—H⋯O and C—H⋯O hydrogen bonds, forming chains parallel to the ab plane in benzohydrazide and O—H⋯O contacts in benzoic acid. The sheets are further stacked through C—H⋯π interactions resulting in the formation of a 3D supramolecular network. Hirshfeld surface analysis has also been performed to investigate intermolecular interactions in the solid-state; the most important contributions for the crystal packing are from H⋯H, C⋯H/H⋯C, and O⋯H/H⋯O interactions. Additionally, DFT calculations with the B3LYP/6-311G (d, p) level of the theory have been used to analyze the Mulliken atomic charges, molecular electrostatic potential map, and non-linear optical properties of the compounds were produced using the optimized structures. Moreover, the natural bond orbital analysis is conducted to explore the interactions among different orbital and lone pairs taking place within the compounds. The energy framework calculations suggest that the contacts formed between molecules are largely dispersive.

A DFT Study on the Mechanism and Origin of Regioselectivity in the Rhodium/Diene‐Catalyzed Ring‐Opening Reactions of C1‐Substituted Oxabenzonorbornadienes with Arylboronic Acids

AbstractThe mechanism and the origin of the regioselectivity of the rhodium/diene‐catalyzed ring‐opening reactions of C1‐substituted oxabenzonorbornadienes with arylboronic acids has been examined using hybrid density functional theory (DFT). The overall mechanism for the reaction is considered as a four‐step reaction including transmetalation, carborhodation, β‐oxygen elimination, and protonolysis. The free energy profiles show that the rate‐determining step is involved in the protonolysis step which differs from previous mechanistic studies on metal‐catalyzed ring‐opening reactions of oxabenzonorbornadienes. Additionally, it is theorized the β‐oxygen elimination step is the origin of regioselectivity. DFT calculations predict the formation of the 1,2,4‐trisubstituted naphthalene framework is selective over the 1,1,2‐trisubstituted product, in agreement with experimental observations.

Rapid construction of cyclopenta[b]naphthalene frameworks from propargylic alcohol tethered methylenecyclopropanes

We have developed a new synthetic methodology for the rapid construction of cyclopenta[b]naphthalene frameworks from the reaction of propargylic alcohol tethered methylenecyclopropanes with mesyl chloride in the presence of triethylamine through cascade cyclization. The reaction can be performed under mild conditions without the use of transition metals, affording the target products in moderate to good yields, and this cyclization reaction process can be scaled up to a gram-scale synthesis.

Heterocyclic Naphthalimides as New Skeleton Structure of Compounds with Increasingly Expanding Relational Medicinal Applications.

Naphthalimide compounds are an important type of nitrogen-containing aromatic heterocycles with cyclic double imides and the naphthalene framework. This π-deficient large conjugated planar structure enables naphthalimide derivatives to readily interact with various biological cations, anions, small molecules and macromolecules such as DNAs, enzymes and recetors in living organism via noncovalent bonds, therefore exhibiting extensive potentiality in relatively medicinal applications. Currently, some naphthalimides as anticancer agents have entered into clinical trials and other naphthalimide-based medicinal developments as potential drugs for treatment of various diseases are actively and unprecedentedly expanding. Naphthalimide-derived artificial ion receptors, fluorescent probes and cell imaging agents are being overwhelmingly investigated and have a diversity of potential applications in real-time detecting ions and biomolecules, understanding biological processes and determining pharmacological and pharmacokinetic properties. All the above mentions have strongly implied that naphthalimide-based derivatives as new skeleton structure of compounds possess increasingly expanding relational medicinal applications, and the related research is becoming a quite attractive active topic and newly rising highlight. Combining with our research and referring other works from literature, this work systematically reviews the current research and development of heterocyclic naphthalimides as anticancer, antibacterial, antifungal, antiviral, anti-inflammatory, antidepressant agents as well as artificial cation and anion receptors, diagnostic agents and pathologic probes, and cell imaging agents for biologically important species. Some rational design strategies, structure-activity relationships and action mechanisms are discussed. The perspectives of the future development of naphthalimide-based medicinal chemistry are also presented.

ChemInform Abstract: Aerobic Dimerization of Enediyne Compounds: Construction of Naphthalene Frameworks.

AbstractA novel bimolecular oxygenative annulation of enediyne compounds leading to naphthalene frameworks is introduced.

Aerobic Access to Highly Substituted Naphthalene Frameworks

Key words cycloaddition - dimerization - enynes - naphthalene frameworks

Aerobic Dimerization of Enediyne Compounds: Construction of Naphthalene Frameworks.

The first bimolecular oxygenative annulation of enediyne compounds leading to naphthalene frameworks has been developed by using Pd(OAc)2 as the catalyst in the presence of NaI under O2 (1 atm). This reaction provided efficient access to a class of symmetric core-annulated naphthalenes by the homoannulation of enediyne-imides. Intriguingly, the crossover annulation of enediyne-imides and other functionalized enediynes could also be achieved by the same catalytic system, resulting in the formation of several unsymmetrical naphthalene derivatives. Preliminary mechanistic investigation using (18) O isotopic labelling and radical scavengers indicated that radical oxygen incorporation cascades might be involved in this conversion.

ChemInform Abstract: Rhodium‐Catalyzed Annulation Between 2‐Arylimidazo[1,2‐a]pyridines and Alkynes Leading to Pyrido[1,2‐a]benzimidazole Derivatives.

AbstractThe method tolerates chloro, bromo, cyano, and methoxycarbonyl groups.

Analysis of CF···FC interactions on cyclohexane and naphthalene frameworks.

Intramolecular CF···FC interactions in selected organofluorine compounds (all-syn-1,2,3,4- and all-syn-1,2,4,5-tetrafluorocyclohexane, 1,8-difluoronaphthalene, 4,5-difluorophenanthrene, 2,2',5,5'-tetrafluorobiphenyl) were studied at the MP2/aug-cc-pVDZ level using the recently developed noncovalent interaction (NCI) method. For the optimized minima, all CF···FC interactions that are identified by this method are classified as attractive, even in those cases where suitable isodesmic reaction energies fail to provide evidence for an energetic stabilization. Possible relations between these interactions and the observable JFF spin-spin coupling constant values are discussed.

ChemInform Abstract: Synthesis of Highly Substituted Pyranonaphthalene Spiroketals Related to the Griseusins Using a Hauser—Kraus Annulation Strategy.

Abstract The synthesis of an advanced pyranonaphthalene spiroketal as an intermediate for the total synthesis of griseusin B is described. A one-pot Hauser–Kraus annulation–methylation via reaction of a highly-substituted enone with a cyanophthalide was employed to construct the naphthalene framework. Other key steps include Sharpless asymmetric dihydroxylation of a ( Z )-alkene and an HF-pyridine mediated double TBS deprotection-spirocyclisation.

Synthesis of highly substituted pyranonaphthalene spiroketals related to the griseusins using a Hauser–Kraus annulation strategy

The synthesis of an advanced pyranonaphthalene spiroketal as an intermediate for the total synthesis of griseusin B is described. A one-pot Hauser–Kraus annulation–methylation via reaction of a highly-substituted enone with a cyanophthalide was employed to construct the naphthalene framework. Other key steps include Sharpless asymmetric dihydroxylation of a (Z)-alkene and an HF-pyridine mediated double TBS deprotection-spirocyclisation.

Structure–property relationship of naphthalene based donor–π–acceptor organic dyes for dye-sensitized solar cells: remarkable improvement of open-circuit photovoltage

Four new donor–π–acceptor organic dyes (YF01–04), containing naphthalene-substituted amines as an electron donor and cyanoacrylic acid as an electron acceptor, were designed and synthesized, and their photophysical properties and dye-sensitized solar cells (DSCs) performances were characterized. Dyes YF02 and YF04, with 2,6-disubstituted naphthalene frameworks, were superior than their analog dyes YF03 and YF01, having 1,2-disubstituted naphthalene moiety, in incident-photo-to-current conversion efficiency (IPCE) and total solar-to-electric conversion efficiency (η). The DSCs based on YF02, comprised of diphenylamine moiety as the donor, produced the highest η of 5.29% compared to 4.03% of the analog dye YF04, which has pyrrolidine as the donor. Remarkably, a high open-circuit photovoltage (Voc) of 0.799–0.807 V was achieved in the cases of YF02–03, which have diphenylamine-donors. To better understand the structure–property relationship for DSCs application, molecular modelling was performed on YF01–04 and vertical electronic excitations were calculated using long-range corrected energy functional WB97XD and CAM-B3LYP at the basis set level DGDZVP, which were in excellent agreement with the experimental results. Moreover, the equilibrium molecular geometries of dyes YF01–04 were calculated at the density function theory (DFT) level using the hybrid energy functional B3LYP and basis set DGDZVP. The torsion angles (θ) between the naphthalene moiety and diphenylamine donor in YF02 and YF03 were more twisted than that of the pyrrolidine-donor dyes YF01 and YF04, precluding efficient intermolecular π–π charge transfer, which translated into high Voc. Compared to the reference dye TA-St-CA, which is based on diphenylamine as an electron donor linked to a phenyl ring, YF02 achieved higher Voc, which indicated that naphthalene substituted with diphenylamine is more efficient in retarding charge recombinations.

Face-to-Face Dimeric Tetrathiafulvalenes and Their Cation Radical and Dication Species as Models of Mixed Valence and π-Dimer States

Abstract Intramolecular interactions of face-to-face tetrathiafulvalenes (TTFs) in 1,8-bis(tetrathiafulvalenyl)naphthalene frameworks were investigated in neutral and cationic states. From X-ray analysis and NMR spectroscopy on neutral 1,8-bis(tetrathiafulvalenyl)naphthalenes, which exist as a mixture of syn- and anti-isomers in solution, there is steric repulsion between TTF moieties. However, analysis of the cyclic voltammogram (CV) revealed that a strong attractive interaction was present in the cation radical state. Electronic spectra of the cation radical state showed the presence of a mixed-valence (MV) state with a strong charge resonance feature. ESR spectra of the 1,8-bis(tetrathiafulvalenyl)naphthalene cation radical showed a typical signal of an MV state. Furthermore, a π-dimer, which exhibits pronounced Davydov splitting in the electronic spectra, was formed in the dication state. The observed absorption bands in the electronic spectra were characterized by using quantum chemical calculations of the cation radical and dication species. NMR spectra of both the π-dimer and tetracation species show either a deshielding effect due to cationic charge or a shielding effect due to diamagnetic ring currents. To our knowledge, this is the first reported example of a 1H NMR spectrum of TTF π-dimer.

Intramolecular Domino Electrophilic and Thermal Cyclization of peri‐Ethynylene Naphthalene Oligomers

The intramolecular electrophilic or thermal cyclization of arylene ethynylene precursors recently became a powerful method for the synthesis of new polycyclic aromatic hydrocarbons (PAHs). In this work, we investigated in detail the synthesis and intramolecular cyclization reaction of a series of peri-ethynylene naphthalene oligomers in which the ethynylene units are fixed in close proximity within the naphthalene framework. The high reactivity of these precursors led to simultaneous thermal cyclization reactions, even during their syntheses. Electrophilic cyclizations with iodine were also undertaken. Several new PAHs containing five-membered rings, for example, indeno[2,1-a]phenalene, acenaphtho[1,2-a]pyrene, and benzo- or naphtho-annulated fluoranthene derivatives, were synthesized and their structures were unambiguously determined by X-ray crystallographic analysis. Plausible mechanisms were proposed and it was demonstrated that oligomers most probably underwent intramolecular domino cyclization via either radical or cationic intermediates. The photophysical and electrochemical properties of these new PAHs were investigated and some of them displayed amphoteric redox behavior, due to the existence of five-membered rings.

An acyclic phane receptor with a pair of disulfonaphthalene arms recognizing 2,3-trans-gallate-type catechins in water

In order to develop a receptor molecule for recognizing differences in catechin structures, complexation between catechins and a water-soluble acyclic phane composed of an isophthalate and two aminodisulfonaphthalenes was investigated with 1H NMR spectroscopy. The phane receptor formed 1:1 complexes with the catechins and showed preferential binding ability for the 2,3-trans-gallate-type catechin. The binding studies demonstrated the length of naphthalene framework required to form a hydrophobic environment for the complexation.

Diamidonaphthalene-supported pnictogenium cations: Synthesis of an N-heterocyclic stibenium cation by a novel protonation route

A 1,8-bis(alkylamido)naphthalene framework has been applied to the construction of N-heterocyclic arsenium and stibenium cations; a novel synthetic route, involving protonation of an ancillary amido ligand, was used to generate the base-stabilized stibenium cation.

New aromatic rearrangement accompanying ring closure of 2-arylpropylidenemalonodinitriles to 1-aminonaphthalene-2-carbonitriles

Cyclization and a rearrangement in concentrated sulfuric acid of 2-(4-substituted-phenyl)propylidenemalonodinitriles ( 1 ) into 1-amino-4-methyl-6-substituted-naphthalene-2-carbonitriles ( 5 ) appears to involve a series of steps such as ipso electrophilic attack of the protonated nitrile function on the para position of the phenyl group, opening of a spirobenzenium cation or its transformation, and ring reclosure to the naphthalene framework with participation of the secondary alkyl carbocation as an active electrophile.