Naphthyl Ethers Research Articles

Optimization of the ultrasound-assisted synthesis of allyl 1-naphthyl ether using response surface methodology

Allyl 1-naphthyl ethers are useful compounds for different purposes, but reported methods to synthesize them require long reaction times. In this work, we have obtained allyl 1-naphthyl ether in good yield using ultrasonic-assisted methodology in a 1-h reaction. A central composite design was used to obtain a statistical model and a response surface ( p < 0.05; R 2 = 0.970; R 2 adj = 0.949; R 2 pred = 0.818) that can predict the optimal conditions to maximize the yield, validated experimentally.

Claisen Rearrangements: Insight into Solvent Effects and “on Water” Reactivity from QM/MM Simulations

An "on water" environment, defined by the absence of water solubility of the reactants, has been reported to provide increased rate accelerations, yields, and specificity for several types of organic reaction classes compared to organic solvents. The aromatic Claisen rearrangements of allyl p-R-phenyl ethers (R = CH(3), Br, and OCH(3)) and allyl naphthyl ether have been investigated to determine the origin of the on water effect using QM/MM Monte Carlo calculations and free-energy perturbation theory. The simulations indicate that on water rate enhancements for the rearrangements are derived from the ability of the interfacial waters to stabilize the polar transition state via enhanced hydrogen bonding at the oil/water interface. The position and orientation of the aromatic ethers at the interface are crucial factors affecting solvent accessibility during the reaction pathway; computed solute-solvent energy pair distributions and radial distribution functions showed that hydrophobic substituents on the solute provided a more polar solvent environment than hydrophilic substituents by tilting the reacting oxygen toward the water surface. Calculations in 16 different solvents accurately reproduced the experimental trend of increased rates correlated to increasing solvent polarity. Hydrophobic effects did not provide a substantial contribution to the lowering of the free energy activation barrier (<0.5 kcal/mol), and solvent polarizability via a polarizable force field was also found to be negligible in the observed rate accelerations. New insight into solvent effects for the Claisen rearrangement is presented herein, and a QM/MM approach for computing reactions on a liquid surface is highlighted.

Regioselectivity Change in the Reaction of Naphthalene and 2-Naphthyl Ethers with 1,3,5-Triazines Depending on Reagent Quantities

A new method for the synthesis of 4H-benzo[de]isoquinolin-4-ones has been developed, based on the reaction of 2-naphthyl ethers with an equimolar quantity of 1,3,5-triazines in polyphosphoric acid. With a 2.5 molar excess of 1,3,5-triazines in polyphosphoric acid, the products of 1,6-diacylation (diformylation) are formed. Isoquino[6′,5′,4′:10,5,6]anthra[2,1,9-def]isoquinoline is formed upon reaction of a 1.5 molar excess of 1,3,5-triazine with naphthalene in polyphosphoric acid at 130-140 ˚C.

A Simple SN2 Reaction for the Undergraduate Organic Laboratory

A simple procedure for the synthesis of n-butyl naphthyl ether is presented. This procedure represents an easy method for the production of an aryl ether by an SN2 reaction, uses ethanol as an environmentally friendly solvent, and does not require the use of a lachrymator. Product isolation is done by pouring the reaction mixture over ice and collecting the solid by suction filtration. Students typically recover from 7–95% of the ether.

Synthesis of New 2-Naphthyl Ethers and Their Protective Activities against DNA Damage Induced by Bleomycin-Iron

The reaction of 2-naphthaloxyacetic acid with thiosemicarbazide in the presence of phosphoryl chloride, followed by treatment with phenacylbromides, led to the formation of imidazo[2,1-b][1,3,4]thiadiazoles 3a-c. 2-(Naphthalen-3-yloxy)acetohydrazide 4 on treatment with ethyl 2-(2-arylhydrazono)-3-oxobutanoates (5a-c), 2-methoxymethylene)malononitrile, or ethyl 2-cyano-3,3-bis(methylthio)acrylate led to the formation of substituted pyrazoles 6-8. The reaction of the hydrazide 4 with hydrazonoyl chlorides 9a-c and 1,2,4,5-benzene tetracarboxylic-1,2:4,5-dianhydride produced bis-diazo compounds 10a-c and dimide 11 respectively. All new compounds were tested for their protective activity against DNA damage induced by bleomycin-iron complex. Compound 2 showed the greatest protection against DNA damage, thus diminishing chromogen formation between the damaged DNA and thiobarbituric acid.

Role of 2-Naphthyl Ether Intermediate in Formation of Isolable Atropisomers Derived from the Coupling Reaction of (2-Hydroxy-3,3-dimethylindolin-1-yl)(substituted Phenyl)methanones with 2-Naphthol

The formation pathway of the atropisomers derived from the reaction of (2-hydroxy-3,3-dimethylindolin-1-yl)(4-substituted phenyl)methanones with 2-naphthol in the presence of BF 3• Et 2 O was discussed on the basis of the isolation of the 2-naphthyl ether intermediate whose structure was determined by single crystal X-ray analysis. The results indicate that the coupling reaction proceeds through stepwise mechanism, i.e., the ether intermediate formation followed by Fries-type rearrangement.

Photochemical Generation and Reactivity of Naphthyl Cations: cine Substitution

AbstractThe photochemical solvolyses of naphthalen‐1‐yl(phenyl)iodonium tetrafluoroborate and naphthalen‐2‐yl(phenyl)iodonium tetrafluoroborate in methanol regiospecifically yield the naphthalen‐1‐ and ‐2‐yl ethers but afford scrambled 1‐ and 2‐phenylnaphthalene Friedel–Crafts products. It is demonstrated that singlet naphthyl cations account for the formation of the naphthyl ethers, but that the cine substitution is most likely to be due to the intermediacy of triplet naphthyl cations. According to the experiments reported here, the singlet naphthyl cations are lower in energy than their triplet isomers. High‐level MO calculations for the cations in methanol support this finding. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

Selective Transport of Water Mediated by Porous Dendritic Dipeptides

The replacement of the benzyl ethers from the periphery of self-assembling dendritic dipeptides with naphthyl ethers provided the simplest mechanism to enhance the thermal stability of their supram...

Solvent Affected Facile Synthesis of Hydroxynaphthyl Ketones: Lewis Acids Promoted Friedel–Crafts and Demethylation Reaction

Hydroxynaphthyl ketones were obtained with high yields under very mild conditions in the presence of AlCl3 via Friedel–Crafts acylation and demethylation from naphthyl ethers. Several Lewis acids were tested, and AlCl3 was the most efficient catalyst.

Bismuth Triflate Catalyzed Claisen Rearrangement of Allyl Naphthyl Ethers.

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Differentiation of Isomeric Substituted Diaryl Ethers by Electron Ionization and Chemical Ionization Mass Spectrometry

A series of isomeric substituted diaryl ethers, i.e., 2- or 4-NO2, 5- FC6H3OC6H4 (4-R), where R=H, COCH3, COOCH3, NO2, CHO, OCH3 etc., which comprise ortho and para isomers with respect to the position of the nitro group are studied under GC-EI-MS and CI-MS conditions. The EI mass spectra of ortho and para isomers show distinct fragment ions, where the [MOH]+ and [MOHO]+ ions specifically appeared in all spectra of the ortho isomers (I), whereas the para isomers (II) contain [MO]+ and [MNO]+ ions. The [MOHCO]+ and [MOHNO]+ ions in I, and [MNO2]+ ion in II are the other specific fragment ions observed but feasibility of these fragment ions are found to depend on the nature of the substituent (R). The substitution (R) effect is also clearly reflected in the formation of fragment ions due to sigma-cleavage process with or without hydrogen migration. Similar differences in the formation of specific fragment ions are also observed in ortho and para isomers of substituted aryl naphthyl ethers. The methane/CI of isomeric compounds resulted in the same set of fragment ions, but prominent differences are observed in the relative abundance of [MHNO]+, which is relatively higher in para isomers compared with corresponding ortho isomer.

Bismuth triflate catalyzed Claisen rearrangement of allyl naphthyl ethers

Bismuth triflate was found to be an efficient catalyst for the Claisen rearrangement of allyl naphthyl ethers. The reaction proceeds smoothly with a catalytic amount of bismuth triflate (20 mol %) to afford the corresponding ortho-allyl naphthol in moderate to good yields in most cases.

Palladium-catalysed reduction of heteroaromatic naphthyl ethers: Structural effects on reactivity

Tetrazolyl and benzisothiazolyl naphthylmethylic ethers 3 and 4( a– e) are stable crystalline compounds that can be synthesised in high yields by reaction of the corresponding naphthyl methanols ( 1a– e) with the derivatizing agents 2a and 2b. Experimental conditions for palladium-catalysed hydrogenolysis of ethers 3, 4, with a hydrogen donor and with molecular hydrogen, were investigated. Analysis of the structure and reactivity indicates that naphthylmethylic ethers 3 and 4 are structurally similar to the corresponding benzyloxyderivatives around the ether bond but exhibit different reactivity. Structural analysis for these compounds is based on crystallographic structure determinations, for 5-(2-naphthylmethoxy)-1-phenyltetrazole ( 3a) and 3-(2-naphthylmethoxy)-1,2-benzisothiazole 1,1-dioxide ( 4a), and molecular orbital DFT(B3LYP)/6-311G(d) calculations, for all ethers. It can be concluded from this investigation that 5-chloro-1-phenyltetrazole 2a acts as a better derivatizing agent for naphthyl methanols than 3-chloro-1,2-benzisothiazole-11-dioxide 2b, this contrasting with what has been observed with phenols, allylic and benzylic alcohols.

Preparation and characterization of zeolite catalysts for etherification reaction

Catalytic etherification of 2-naphthol with ethanol has been carried out over a series of solid-acid catalysts such as H-Beta, H-MOR and H-ZSM-5 using a flow-type reactor. H-Beta zeolite shows higher conversion and catalytic stability than other catalysts for the production of 2-naphthyl ethyl ether, which may be correlated to the amount and strength of acid sites. H-Beta zeolites with different Si/Al ratios show that conversion decreases with increasing Si/Al ratios. The NH 3-TPD profiles indicate that the weak acidity decreases more sharply with increase in Si/Al ratios, compared with the strong acidity. The influences of ethanol/2-naphthol molar ratios, reaction temperature, and space velocity with respect to catalytic activities are investigated for H-Beta zeolite in the present work.

Fluorescent quenching of the 2-naphthoxide anion by aliphatic and aromatic halides. Mechanism and consequences of electron transfer reactions.

The fluorescent excited state of the 2-naphthoxide ion (1) is quenched by aliphatic and aromatic halides according to an electron-transfer mechanism, with generation of the corresponding alkyl and aryl radicals by a concerted or consecutive C-X bond fragmentation reaction. Whereas bromo- and iodobenzene follow a concerted ET mechanism (C-X, BDE control), 1-bromonaphthalene exhibits a stepwise process (pi LUMO control). The photoinduced reaction of anion 1 with 1-iodoadamantane (2) in DMSO affords substitution products on C3, C6, and C8, 1-adamantanol, 1-adamantyl 2-naphthyl ether, and adamantane (3.2, 13.2, 12.2, 2.8, 2.5, and 14.1% yields, respectively). A complex mixture is also observed in the photochemical reaction of neopentyl iodide (3) with anion 1, which renders substitution on C1, C3, C6, C8, and 2-naphthyl neopentyl ether (8.1, 1.3, 19.1, 31.1, and 2.8% yields, respectively). The absence of reaction in the dark and the inhibition of the photoinduced reaction by the presence of the radical traps di-tert-butylnitroxide (DTBN) and 1,4-cyclohexadiene are evidence of a radical chain mechanism for these substitutions. On the other hand, only coupling at C1 is achieved by the photostimulated reaction of anion 1 with iodobenzene (5), to afford 41.9% of 1-phenyl-2-naphthol and 5.4% of disubstitution product. The regiochemistry of these reactions can be ascribed to steric hindrance and activation parameters.

Nucleofuge effect : the kinetic and mechanistic studies of the reactions of some O-aryloximes and phenyl naphthyl ether with n-butylamine in acetonitrile

The aminolysis reactions of O-(2',4'-dinitrophenyl)-2-naphthol (DNPN), O-(2',4'-dinitrophenyl)indanoneoxime (DNPIO), and O-(2,4-dinitrophenyl)propanoneoxime (DNPPO) have been carried out with n-butylamine in acetonitrile at 35 ′ 0.1°. The coloured product obtained in each case was N-(2,4-dinitrophenyl)butylamine, in addition, in the case of DNPN, 2-naphthol was also obtained in quantitative yield. Second order rate constant, k A increases linearly with increase in the base concentration. Mild catalysis has been observed during the reaction of n-butylamine with DNPN while no catalysis has been observed in the case of DNPIO and DNPPO. The observed order of reactivity is : DNPN > DNPIO > DNPPO. Mechanistic interpretation is given.

The Development of a Convergent and Efficient Enantioselective Synthesis of the Bengamides via a Common Polyol Intermediate

AbstractAn efficient, general synthetic route to the bengamide family of antitumor agents from a common polyol thioester is described. Consecutive aldol condensations afford the protected polyol thioester side chain suitable for coupling to the bengamides. A novel chiral‐phase‐transfer‐catalyzed enantioselective alkylation affords the properly functionalized caprolactams required for the synthesis of more‐complex members of the bengamide family. Use of the methyl 2‐naphthyl ether protecting group, compatible with the boron Lewis acids required for enantioselective aldol condensation, allows direct access to all the bengamides.

Aromatic Side Chain-Functionalized Long Chain Acid Salts: Structural Factors Influencing Their Lyotropic Liquid-Crystalline Behavior

The structural factors influencing the self-assembly of aromatic side chain functionalized long chain acid salts into lyotropic liquid crystal (LLC) phases were examined. Two sets of amphiphiles were synthesized containing two different ionic headgroups (i.e., sodium carboxylate and sodium sulfonate) and four different aromatic side chains (i.e., 4-styryl ether, 4-ethylphenyl ether, 1-naphthyl ether, and 4-phenylazophenyl ether) positioned at various locations along the amphiphile backbone. Systematic variation of the type of the aromatic side chain and its relative position on the amphiphile as a function of the two headgroups revealed that the position of the side chain on the amphiphile is the most important structural factor influencing the type and stability of the LLC phases formed. The nature of the aromatic side chain and the nature of the anionic headgroup play much more subtle roles in the LLC behavior of this particular amphiphile structural motif. Noncovalent aromatic−aromatic interactions are known to play important roles in the aggregation behavior of amphiphiles containing aromatic units along the alkyl chains; however, such interactions could not be detected spectroscopically in the LLC phases of our aromatic side chain amphiphiles. We speculate that the differences in alkyl chain interdigitation and packing efficiency arising from having the aromatic unit as a side chain rather than along the alkyl chains are responsible for this discrepancy. Control experiments with aliphatic ether side chain amphiphiles also corroborate the fact that aromatic interactions do not play a significant role in the aggregation behavior of these side chain amphiphiles. Side chain amphiphiles lacking an aromatic unit are still able to form the inverted hexagonal LLC phase, so long as the extent of branching and volume of the aliphatic side chain are sufficient.

Thermodynamics and kinetics of homolytic cleavage of carbon–oxygen bonds in radical anions obtained by electrochemical reduction of alkyl aryl ethers

The properties and the reactivity of the radical anions of 4-cyanophenyl alkyl ethers and naphthyl alkyl ethers have been determined by electrochemical methods. Under electrochemical conditions homolytic dissociation is the only observed process. Cyclic voltammetry studies lead to the conclusion that this process is a stepwise one, the initially produced radical anion cleaving by a slow first order reaction followed by a second electron transfer in a DISP1 mechanism. A Marcus type relationship between the cleavage rate constants and the standard free energy of the reaction leads to an intrinsic barrier in the range of 0.7 to 0.8 eV. The analysis of the intrinsic barrier values indicates that solvent organisation represents a modest contribution, the bond dissociation energy of the radical anion (structural contribution) being the main factor in the total barrier. Previously unknown bond dissociation energies of naphthyl ethers have been estimated using the correlations established in this work.

FURTHER STUDY OF ALLYL ETHERS AND RELATED COMPOUNDS AS TRANSFER AGENTS IN RADICAL POLYMERIZATIONS

Allyl glycidyl ether (AGE), allyl 1,1,2,3,3,3-hexafluoropropyl ether (AFE), allyl 2-naphthyl ether (ANE), 2-vinyl-1,3-dioxolane (2VD) and allyl alcohol (AA) have been examined as transfer agents in the radical polymerization of methyl methacrylate (MMA) at 60°C; the transfer constants are 1.1 × 10−3, 0.1 × 10−3, 0.2 × 10−3, 1.1 × 10−3 and 0.6 × 10−3, respectively. AFE and AA barely affect the rate of polymerization: AGE, ANE, and 2VD act as weak retarders. There is no direct correlation between effectiveness as a transfer agent and the extent of retardation for these additives. For copolymerization with MMA (monomer-1), the monomer reactivity ratios r1 are 42 ± 5 and 32 ± 5 for AGE and ANE, respectively; for both cases, r2 is very close to zero; 2VD engages in copolymerization with MMA to a negligible extent. Experiments involving styrene or acrylonitrile gave results consistent with those obtained using MMA.