A facile method for synthesis of polysubstituted naphthalene derivatives through pyrrolidine catalyzed domino reaction

A novel synthetic method for polysubstituted naphthalene derivatives via a pyrrolidine-mediated cascade Michael/Henry reaction was developed, in which easily prepared 2-(2-oxoethyl)benzaldehydes and nitroalkenes were employed as the starting materials. The reaction consists of four consecutive reactions that include a cascade Michael/Henry reaction, a dehydration reaction, and an aromatization reaction in one pot to afford synthetically important naphthalene derivatives with moderate yields.     

Ytterbium(III) Triflate as an Efficient Catalyst for the Synthesis of Perimidine Derivatives under Mild Conditions

Various biologically important perimidine derivatives have been efficiently synthesized in excellent yields using naphthalene‐1,8‐diamine with various ketones in the presence of a catalytic amount of Yb(OTf)₃. The influence of the loading of Yb(OTf)₃, reaction solvent, the structure of ketones was studied. This method is a very easy, simple and high yielding reaction for the synthesis of perimidine derivatives.     

Formation of azulene and naphthalene from piperylene

Piperylene mixed with air is converted into a mixture of aromatics containing azulene and naphthalene on contact with bisnuith oxide at -600 °C. The yield of azulene and naphthalene is 6–8 %, The reaction is accompanied by burning of some of the piperylene and by the reduction of Bi₂O₃ to Bi metal. When the initial mixture is diluted with steam no reduction occurs. The reaction is believed to involve elimination of the allylic hydrogen, formation of dienyl radicals, their dimerization, and subsequent aromatization.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1556–1558, June, 1996.     

Carbonylation of diols and their ethers and esters with ruthenium catalysts: synthesis of lactones and hydroxyacids ethers and esters

Diols and their formic or acetic esters can be carbonylated to give lactones or the corresponding hydroxyacid esters of ethers in the presence of carbonylruthenium iodide systems, [Ru(CO)₃I₃]⁻/alkyl or metal iodide, at a temperature of 200°C and CO pressure of 10-20 MPa. The reaction in the case of 1,3-propanediol gives γ-butyrolactone, with a selectivity of 60-% . Side reactions of homologation to 1,4-butanediol derivatives and hydrogenolysis to n-propyl derivatives by H₂ produced by the water gas shift reaction (WGSR) also occur, together with acid-catalyzed dehydration to give linear polypropylene glycols, α,ω-diols with more than 3 carbon atoms in the chain preferentially give hydroxyacid esters and ethers.The cyclic ether by-products and linear polyether by-products can be further activated and carbonylated under the reaction conditions to give lactones or hydroxy-acid derivatives thus increasing the total yield of carbonylation products. The formation of H₂ by WGSR involving water produced by the acid-catalyzed dehydration reactions, and the subsequent hydrogenolysis and homologation reactions cannot be avoided.     

Synthesis of Dendritic Phenol Ether Derivatives with a Naphthalene Core

A series of dendritic phenol ether derivatives with a naphthalene core were synthesized by the Williamson reaction as a coupling reaction between 1‐hydroxymethylnaphthalene and polyether‐based dendritic fragments in the presence of phase‐transfer catalyst and alkali. The modified method for chlorination of dendritic benzyl alcohol was also developed using PPh₃ and CCl₄ as reagents and CH₂Cl₂/CCl₄ as solvent.     

Synthesis of naphthalene derivatives through inexpensive BF3·Et2O-catalyzed annulation reaction of arylacetaldehydes with arylalkynes

An inexpensive BF3·Et2O-catalyzed annulation reaction of arylacetaldehydes with arylalkynes has been developed. Various substituted phenylacetaldehydes and phenylacetylenes can undergo this reaction, producing corresponding α-aryl substituted naphthalene derivatives. Use of inexpensive and readily available BF3 ·Et2O catalyst constitutes the most attractive advantage of this transformation.     

Mn(III)acetate-mediated additions of active methylene compounds to bicyclic olefins: Synthesis of bicyclic olefin-fused dihydrofurans

Bicyclic alkenes such as benzonorbornadiene, oxabenzonorbornadiene, norbornene, and norbornadiene were reacted with 1,3-cyclohexanedione and ethyl acetoacetate in the presence of Mn(OAc)₃ and Cu(OAc)₂. Except for the reaction of benzonorbornadiene and ethyl acetoacetate, dihydrofuran derivatives were the only products obtained. The formation of naphthalene derivatives was observed together with dihydrofuran in the aforementioned benzonorbornadiene/ethyl acetoacetate reaction. Additionally, the dihydrofuran product from the addition of ethyl acetoacetate to norbornadiene was slowly converted into epoxide derivative with air. The mechanism for the formation of the products is discussed.     

Synthesis of a Stable Selenoaldehyde by Self‐Catalyzed Thermal Dehydration of a Primary‐Alkyl‐Substituted Selenenic Acid

The unprecedented dehydration of a selenenic acid (RCH₂SeOH) to a selenoaldehyde (RCH?Se) has been demonstrated. A primary‐alkyl‐substituted selenenic acid was synthesized for the first time by taking advantage of a bulky cavity‐shaped substituent. Upon heating in solution, the selenenic acid underwent thermal dehydration to produce a stable selenoaldehyde, which was isolated as stable crystals and crystallographically characterized. Investigation of the reaction mechanism revealed that this β dehydration reaction involves two processes, both of which reflect the characteristics of a selenenic acid: 1) dehydrative condensation of two molecules of selenenic acid to generate a selenoseleninate intermediate [RCH₂SeSe(O)CH₂R], an isomer of a selenenic anhydride, and 2) subsequent β elimination of the selenenic acid from this intermediate to form a C?Se double bond, which establishes the self‐catalyzed β dehydration of the selenenic acid.     

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 ¹⁸O isotopic labelling and radical scavengers indicated that radical oxygen incorporation cascades might be involved in this conversion.     

Pseudopolymorphism and phase stability of 7-piperidino-1,2,3,5-tetrahydroimidazo-[2,1-b]quinazolin-2-one (DN-9693)

The phase stabilities of three pseudopolymorphs of DN-9693 were studied by using thermogravimetry and differential thermal analysis. The thermal dehydration of DN-9693·2HCl·H₂O proceeds by the mechanism of two-dimensional growth of nuclei. The thermal dehydration of 0.5 mol of H₂O per mol of DN-9693·2HCl·2H₂O, and that of 2 mol of H₂O per mol of DN-9693·2HCl·3H₂O, proceed by the mechanisms of three-dimensional diffusion and three-dimensional phase boundary reaction, respectively, but the dehydration followed overlaps with the thermal elimination of HCl. The half-lives for the dehydration at 25°C show that DN-9693·2HCl·H₂O is the most stable form.     

Mass fragmentation and structure of siphonaxanthin,siphonein and derivatives

High resolution mass spectrometry has been employed to establish the structural formulae of the unique carotenoid pigment siphonaxanthin, its natural ester, siphonein and several derivatives. Siphonaxanthin exhibits a fragmentation reaction that is unusual among carotenoid pigments, namely, the elimination of carbon dioxide, observed as [M - CO₂] and [M - (CO₂ + H₂O)]. This reaction involves the migration of an oxygen atom. Siphonaxanthol, a partially hydrogenated siphonaxanthin, exhibits a similar reaction involving the elimination of carbon monoxide and formaldehyde. From the fragmentation of derivatives of siphonaxanthin, such as the triacetate, the dimethyl ether and siphonaxanthol, and also from the fragmentation of related pigments, such as loroxanthin and fucoxanthin, the unique structural units responsible for the elimination of the carbon dioxide and carbon monoxide have been identified.     

Reaction of Dess-Martin periodinane with 2-(alkylselenyl)pyridines. Dehydration of primary alcohols under extraordinarily mild conditions

Dess-Martin periodinane oxidizes very rapidly 2-pyridylseleno derivatives RR′CHCH₂SePy in CHCl₃ or CH₂Cl₂ and more chemoselectively than mCPBA. Tetravalent selenanes, RR′CHCH₂Se(OAc)₂Py, seem to be formed. Treatment of these intermediates with aqueous NaHCO₃ gives rise to irreversible hydrolysis and elimination to terminal alkenes. As the OH/SePy exchange can be performed in minutes, the overall process is an exceptionally efficient procedure for the dehydration of primary alcohols.     

Pd-Catalyzed Annulation of 1-Halo-8-arylnaphthalenes and Alkynes Leading to Heptagon-Embedded Aromatic Systems

A palladium-catalyzed heptagon-forming annulation reaction between 1-halo-8-arylnaphthalene and diarylacetylene is reported. The reaction is promoted using a catalytic system comprised of Pd(OAc)₂, moderately electron-deficient triarylphosphine P(4-ClC₆H₄)₃, and Ag₂CO₃ to afford benzo[4,5]cyclohepta[1,2,3-de]naphthalene derivatives in moderate to good yields, in preference to fluoranthene as a competing byproduct. Twofold annulation can also be achieved to access a novel heptagon-embedded polycyclic aromatic hydrocarbon compound.     

A one-step conversion of isoquinolinium salts into naphthalene derivatives1

Berberine chloride (1) upon treatment with NaOAc-Ac₂O yields naphthalene derivatives 4 and 5 In like fashion, 8 gives naphthalene 10; isoquinoline methiodide leads to β-naphthyl acetate; and 12 provides 14. The reaction has been extended to the 3-carbonyl pyridinium series where 3-acetylpyridine methiodide and 3-pyridinecarboxaldehyde methiodide furnish lactones 16 and 17, respectively. All these transformations proceed by initial nucleophilic attack of the acetic anhydride anion on the immonium carbon atom.     

Spectrometrie de Masse du Dimethoxy-2,6 Naphtalene et de Certains de ses Derives

The mass spectra of 2,6-dimethoxynaphthalene and 14 of its derivatives are reported. The fragmentation patterns proposed to account for the main peaks observed are frequently based on the presence of the appropriate metastable peaks. The fragmentation is initiated by the cleavage of an O? CH₃ bond. The molecular ion is the most intense ion in each case and it does not appear to directly eliminate a methoxy group or a substituent directly attached to the naphthalene ring. With NO₂ as a substituent the elimination of nitric oxide from the molecular ion has been observed and confirmed by peak matching.     

Rapid synthesis,kinetics and thermodynamics of binary Mn<Subscript>0.5</Subscript>Ca<Subscript>0.5</Subscript>(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript> · H<Subscript>2</Subscript>O

The non-isothermal kinetics of dehydration of AlPO₄·2H₂O was studied in dynamic air atmosphere by TG–DTG–DTA at different heating rates. The result implies an important theoretical support for preparing AlPO₄. The AlPO₄·2H₂O decomposes in two step reactions occurring in the range of 80–150 °C. The activation energy of the second dehydration reaction of AlPO₄·2H₂O as calculated by Kissinger method was found to be 69.68 kJ mol⁻¹, while the Avrami exponent value was 1.49. The results confirmed the elimination of water of crystallization, which related with the crystal growth mechanism. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the dehydration reaction are calculated by the activated complex theory. These values in the dehydration step showed that it is directly related to the introduction of heat and is non-spontaneous process.     

Cooperative Reductive Elimination: The Missing Piece in the Oxidative‐Coupling Mechanistic Puzzle

The reaction between benzoic acid and methylphenylacetylene to form an isocoumarin is catalyzed by Cp*Rh(OAc)₂ in the presence of Cu(OAc)₂(H₂O) as an oxidant and a leading example of oxidative‐coupling reactions. Its mechanism was elucidated by DFT calculations with the B97D functional. The conventional mechanism, with separate reductive‐elimination and reoxidation steps, was found to yield a naphthalene derivative as the major product by CO₂ extrusion, contradicting experimental observations. The experimental result was reproduced by an alternative mechanism with a lower barrier: In this case, the copper acetate oxidant plays a key role in the reductive‐elimination step, which takes place through a transition state containing both rhodium and copper centers. This cooperative reductive‐elimination step would not be accessible with a generic oxidant, which, again, is in agreement with available experimental data.     

Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides

A cross‐coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr₃ took place to give the corresponding α‐alkenyl esters. GaBr₃ showed the most effective catalytic ability, whereas other metal salts such as BF₃?OEt₂, AlCl₃, PdCl₂, and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti‐carbogallation among GaBr₃, an enol derivative, and a silyl ketene acetal, followed by syn‐β‐alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover‐limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn‐β‐alkoxy elimination and anti‐carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon?oxygen bond in the β‐alkoxy elimination process, which is the turnover‐limiting step in the reaction between a vinyl ether and a silyl ketene acetal.     

Stereochemistry of Hydride Reduction of 20-Hydroxyecdysone Derivatives

The 6-oxo group in 2,3:20,22-di-O-isopropylidene derivatives of 20-hydroxyecdysone and its 24,25/25,26-anhydro analog is reduced with NaBH₄-CeCl₃ in a stereoselective fashion to afford the corresponding 6α-alcohols. In the first case, the reaction is accompanied by dehydration to give Δ¹⁴-bond. Reduction of the same substrates with NaBH₄ or LiAlH₄ in the absence of CeCl₃ leads to mixtures of 6α- and 6β-hydroxy derivatives, the latter prevailing. In all cases, epimerization at C⁵ occurs.     

Beryllium‐Based Anion Sponges: Close Relatives of Proton Sponges

Through the use of high‐level ab initio and density functional calculations it is shown that 1,8‐diBeX‐naphthalene (X=H, F, Cl, CN, CF₃, C(CF₃)₃) derivatives behave as anion sponges, very much as 1,8‐bis(dimethylamino)naphthalene derivatives behave as proton sponges. The electron‐deficient nature of the BeX substituents, which favors strong charge transfer from the anion towards the former, results in anion affinities that are among the largest ones reported for single neutral molecules.