Aromatic annelation. Synthesis of naphthalenes

An efficient cationic cyclization reaction has been developed to prepare substituted naphthalenes. The method has been used to prepare a phenanthrene and will be useful for the synthesis of polynuclear aromatic hydrocarbons and C-glycosyl anthraquinones.     

Conformational properties of the calix[4]naphthalenes

The base-catalyzed condensation of 1-naphthol and formaldehyde in refluxing dimethylformamide affords three isomeric cyclic tetramers which are conformationally flexible over a wide temperature range. Their tetrabenzoate esters however show restricted flexibility. Variable-temperature NMR and low-temperature COSY is used to analyze the conformational preferences of these calix[4]naphthalenes.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Reactivity of 4-halogeno 1-vinyl naphthalenes in cationic polymerization

Improved methods for the synthesis of 4-halogeno 1-vinylnaphthalenes are proposed. Reactivity ratios are determined for the following systems: 4-fluoro-1-vinyl naphthalene-styrene, 4-chloro-1-vinyl naphthalene-styrene, and 4-bromo-1-vinyl naphthalene-styrene. The determinations are performed at various specific temperatures and the relative activation parameters are obtained. It appears that the reactivity of 1-vinyl naphthalene is drastically decreased when substituted by a halogen. In the case of 1-vinyl naphthalene the selection is enthalpically controlled.     

Intermolecular dearomative [4 + 2] cycloaddition of naphthalenes via visible-light energy-transfer-catalysis

The dearomative cycloaddition reaction serves as a blueprint for creating sp³-rich three-dimensional molecular topology from flat-aromatic compounds. However, severe reactivity and selectivity issues make this process arduous. Herein, we describe visible-light energy-transfer catalysis for the intermolecular dearomative [4 + 2] cycloaddition reaction of feedstock naphthalene molecules with vinyl benzenes. Tolerating a wide range of functional groups, structurally diverse 2-acyl naphthalenes and styrenes could easily be converted to a diverse range of bicyclo[2.2.2]octa-2,5-diene scaffolds in high yields and moderate endo-selectivities. The late-stage modification of the derivatives of pharmaceutical agents further demonstrated the broad potentiality of this methodology. The efficacy of the introduced methods was further highlighted by the post-synthetic diversification of the products. Furthermore, photoluminescence, electrochemical, kinetic, control experiments, and density-functional theory calculations support energy-transfer catalysis.

Constructing 3D molecular scaffolds from aromatic hydrocarbons is challenging. Herein, we report dearomative [4 + 2] cycloaddition reaction of naphthalenes via visible-light EnT catalysis which overcomes issues of unfavorable thermodynamics, low yields, and selectivity.     

Thermodynamic functions for halogenated naphthalenes

Thermodynamic functions (heat capacity, enthalpy, entropy and free energy) have been calculated for naphthalene and 11 halogenated naphthalenes in the ideal gas state from 273.15 to 1200 K at 1 atm pressure. All the functions were obtained by statistical—mechanical calculation methods. Agreement with experimental results, where such are available, is satisfactory.     

Mesomorphic properties of some 6-n-alkyl-2-(4′-cyanophenyl)naphthalenes. Preliminary Communication

The synthesis of the title compounds 4 is described and their transition temperatures are compared with the nematic phases of the respective 6-n-alkoxynaphthalene derivatives.     

1,1-Carboboration route to substituted naphthalenes

1,2-Bis(alkynyl)benzene derivatives react with strongly electrophilic boranes to yield in boryl-functionalized bulky naphthalene derivatives by means of a sequence of 1,1-carboboration reactions. These substrates can be functionalized by transition metal catalyzed cross-coupling reactions.     

Gold-catalyzed double migration-benzannulation cascade toward naphthalenes

A novel gold(I)-catalyzed cycloisomerization of propargylic esters leading to unsymmetrically substituted naphthalenes has been developed. This cascade reaction involves an unprecedented tandem sequence of 1,3- and 1,2-migration of two different migrating groups. It is believed that this transformation likely proceeds via the formation of 1,3-diene intermediate or its precursor, which upon cyclization and aromatization steps transforms into the naphthalene core.     

Proton magnetic resonance spectra of monosubstituted naphthalenes

The chemical shifts and coupling constants for the ring protons of fourteen monosubstituted naphthalenes in carbon tetrachloride solution have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Studies at several concentrations have enabled shifts extrapolated to infinite dilution to be obtained and concentration effects arising from solute–solute interactions to be determined.     

Oxciplex emission of naphthalenes in polymer matrices

In this communication we report the observation of oxciplex emission, (T₁ + O₂(¹Δ)) → (S₀ + O₂(³Σ)) + hν from naphthalene and octafluoronaphthalene in polystyrene fluffs. We detect this emission as an oxygen induced luminescence burst upon admission of oxygen to a phosphorescing sample. The assignment is based on a mirror image relationship of the emission to the absorption, and energetic, kinetic, and intensity considerations.     

Diastereo- and enantioselective dearomatization of rhenium-bound naphthalenes

Dihapto-coordinated naphthalene complexes of the form TpRe(CO)(L)(eta(2)-naphthalene) (L = PMe(3), pyridine, or 1-methylimidazole) undergo electrophilic addition with dimethoxymethane and with various Michael acceptors to generate 1H-naphthalenium species. These naphthalenium complexes undergo intra- or intermolecular nucleophilic addition reactions with stabilized enolates, silyl ketene acetals, or enols to form the corresponding dihydronaphthalene complexes. Oxidative decomplexation generates the free dihydronaphthalene. When a resolved form of the rhenium dearomatization agent is used, these reactions can be performed enantioselectively. DFT calculations provide a useful guide in explaining the observed stereochemistry. Depending on reaction conditions, a Michael-Michael ring-closure sequence (MIMIRC) or a net [2 + 4] cycloaddition with the bound naphthalene is also observed, and the corresponding tricyclic molecules can be removed from the metal in high yield.     

Zero-field splitting in phosphorescent triplet states of aromatic hydrocarbons IV. Phenyl naphthalenes

The zero-field splitting parameters D, E, and D* are calculated theoretically for four phenyl naphthalenes. Esr measurements show that the theoretical calculations are in good agreement with experiment. Comparison of the theoretical and experimental results gives some insight into the geometry of these molecules in their lowest triplet state.