N-phenacylpyridinium Bromides Research Articles

Stereoselective Synthesis of Multifunctional Spirooxindole-Dihydrofuran Derivatives

A facile and efficient protocol for the diastereoselective synthesis of novel spirooxindole-dihydrofurans has been developed by the three-component condensation of isatin derivatives, 3-cyanoacetyl indole, and N-phenacylpyridinium bromide in the presence of triethylamine base. The reaction was carried out in ethanol under reflux conditions, and various dihydrofuranyl spirooxindoles were obtained in high yields with good to excellent stereoselectivity.

Efficient microwave-assisted diastereoselective synthesis of indole-based 4,5-dihydrofurans via a one-pot, three-component reaction in water

The combination of two or more different heterocyclic moieties in a single molecule would enhance biological activity significantly. The indole and furan scaffolds are promising candidates in drug design, and they have been widely found in natural products and therapeutic agents. Owing to their pharmaceutical importance, there is an urgent need to design rapid, efficient and environmentally benign protocols for the synthesis of indole–dihydrofuran biheterocycles. Herein, we have developed a novel ecofriendly approach for the diastereoselective synthesis of indole-based 4,5-dihydrofurans through a three-component reaction of 3-cyanoacetyl indoles with various aldehydes and N-phenacylpyridinium bromides in the presence of potassium carbonate as an inexpensive and non-toxic base in water under low power microwave irradiation. The findings show that aromatic and heteroaromatic aldehydes tolerated well in this reaction. The products were obtained in 85–98% yields in 4–20 min. The advantages of this method consist of the environmental friendly reaction conditions, use of green solvent and safe base, availability of raw materials, wide range of usable substrates, short reaction times, excellent yields and absence of any tedious workup or purification.

Solvent-free synthesis of highly functionalized indole-based 4,5-dihydrofurans and evaluation of their antioxidant activity

Facile and efficient diastereoselective synthesis of trans-indolyldihydrofurans by three-component reaction of 3-cyanoacetyl indoles with various aromatic aldehydes and N-phenacylpyridinium bromides in presence of 1,1,3,3-N,N,N′,N′-tetramethylguanidine under solvent-free conditions is described. This ecofriendly protocol offers several advantages such as a cost-effective procedure with excellent yield, short reaction time, ease workup and product isolation, good functional group tolerance, and broad scope of usable substrates. The synthesized compounds were also evaluated for their antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay.

Three-component synthesis of quinolone derivatives bearing 1,3-indandione moiety using pyridinium salts

A series of 3,4-disubstituted dihydroquinolin-2(1H)-ones have been synthesized via three-component reaction of 1,3-indandione with isatin derivatives and N-phenacyl pyridinium bromide salts in presence of triethylamine as basic reagent. This procedure affords a highly efficient route for accessing quinolones by ring expansion of isatin via a one-pot pathway. Products were obtained in good to moderate yield without requiring a chromatographic purification step.

Convenient synthesis of 1a,1b,2,5-tetrahydro-1H-5a-aza-cyclopropa[a]indenes by base promoted cyclodimerization of 1,1-dicyano-2-aryl-3-benzoylcyclopropanes

1,1-Dicyano-2-aryl-3-benzoylcyclopropanes in acetonitrile in the presence of triethylamine underwent cyclodimerization reaction to afford the novel polyfunctionalized 1a,1b,2,5-tetrahydro-1H-5a-aza-cyclopropa[a]indenes in moderate yields. These polycyclic compounds can be more conveniently synthesized by the one-pot domino reaction of N-phenacylpyridinium bromides with arylidene malononitriles.

ChemInform Abstract: Efficient Synthesis of Spiro[furan‐3,3′‐indoline] Derivatives via Reactions of Pyridinium Salts with Isatinylidene Acetoacetates.

An efficient synthetic procedure for the functionalized spiro[furan-3,3′-indoline] derivatives was successfully developed by domino reactions of N-phenacylpyridinium bromides or N-ethoxycarbonylmethylenepyridinium bromide with isatinylidene acetoacetate in the presence of triethylamine in ethanol at room temperature. The mechanism included sequential Michael addition of the in situ generated pyridinium ylide and intramolecular substitution of enolate.

Exploring Spectroscopic and Physicochemical Properties of New Fluorescent Ionic Liquids

In the current study, spectroscopic and physicochemical properties of newly prepared ionic liquids were investigated. Ionic liquids were synthesized via a simple and straightforward route using a metathesis reaction of either N,N-diethyl-p-phenylenediamine monohydrochloride or N-phenacylpyridinium bromide with bis(trifluoromethane)sulfonimide lithium in water. High yield and purity were obtained for the resultant ionic liquids. Data acquired by use of (1)H NMR and FT-IR measurements were consistent with the chemical structures of newly prepared ionic liquids. Results of thermal gravimetric analysis also implied that these ionic liquids have good thermal stability. In addition, UV-vis and fluorescence spectroscopy measurements provided that new ionic liquids are good absorbent and fluorescent. Time-based fluorescence steady-state measurements showed that ionic liquids have high photostability against photobleaching. For a deeper mechanistic understanding of the analytical potential of newly synthesized ionic liquids, spectroscopic and physicochemical parameters, including singlet absorption, extinction coefficient, fluorescence quantum yield, Stokes shift, oscillator strength and dipole moment, were also investigated.

N-Phenacylpyridinium bromides in the one-pot synthesis of 2,3-dihydrofurans

A one-pot three-component process for the synthesis of highly functionalized 2,3-dihydrofurans from 1,3-dicarbonyl compounds, aromatic aldehydes, and N-phenacylpyridinium bromides has been developed. Benzylidene 1,3-dicarbonyl compounds could be generated in situ from aromatic aldehydes and 1,3-dicarbonyl compounds and then reacted smoothly with N-phenacylpyridinium bromides to produce 2,3-dihydrofurans in moderate to good yields. Piperidine/acetonitrile is the optimal condition for this process. To increase the efficiency of this reaction, this one-pot process was also conducted solvent-free under classical heating conditions and grinding conditions.

ChemInform Abstract: Microwave‐Assisted, One‐Pot Reaction of Pyridines, α‐Bromoketones and Ammonium Acetate: An Efficient and Simple Synthesis of Imidazo[1,2‐a]pyridines.

A novel and efficient synthesis of imidazo[1,2-α]pyridines is described. N-Phenacylpyridinium bromides, which were prepared in situ from the addition of pyridines to α-bromoketones, undergo nucleophilic addition of ammonium acetate under microwave irradiation and solvent-free conditions to afford the corresponding imidazo[1,2-α]pyridines in excellent yields.

Microwave-Assisted, One-Pot Reaction of Pyridines, α-Bromoketones and Ammonium Acetate: An Efficient and Simple Synthesis of Imidazo[1,2-a]-pyridines

A novel and efficient synthesis of imidazo[1,2-a]pyridines is described. N-Phenacylpyridinium bromides, which were prepared in situ from the addition of pyridines to α-bromoketones, undergo nucleophilic addition of ammonium acetate under microwave irradiation and solvent-free conditions to afford the corresponding imidazo[1,2-a]pyridines in excellent yields.

A Convenient One-Pot Synthesis of Some New 3-(2-Phenyl-6-(2-thienyl)-4-pyridyl)hydroquinolin-2-ones Under Microwave Irradiation and Their Antimicrobial Activities

A series of 3-(2-phenyl-6-(2-thienyl)-4-pyridyl)hydroquinolin-2-ones 4a–o were synthesized in high yields by a one–pot cyclocondensation reaction under Kröhnke's reaction conditions using 2-chloro-3-formyl quinoline 1a–c, 2-acetyl thiophene 2, and various N-phenacylpyridinium bromides 3a–e in a mixture of ammonium acetate and acetic acid by microwave irradiation. All the compounds have been characterized by elemental analysis, FT-IR, 1H NMR, and 13C NMR spectral analysis. These compounds have been screened for their antimicrobial activities. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Direct ortho‐Arylation of N‐Phenacylpyridinium Bromide by Palladium‐Catalyzed CH‐Bond Activation

A novel palladium catalyzed direct ortho-arylation of N-phenacylpyridinium bromide was developed. The amazing N-phenacyl group regioselectively activates the C-H bond of pyridine and automatically departs from the arylated products. A kinetic isotope effect study proved that the reaction went through a C-H-bond activation pathway and 2,6-diphenylpyridine was produced stepwise from 2-phenylpyridine.

New Substituted Indolizines by 1,3-Dipolar Cycloaddition VI. 7-(4-Nitrobenzyl)indolizines

New indolizine derivatives 6 and 7 containing a 4-nitrobenzyl group attached to the pyridinic ring are obtained by the reaction of N-phenacylpyridinium bromides 3 with 3-butyn-2-one, methyl and ethyl propiolate in 1,2 epoxypropane medium. The compounds structure was assigned by elemental analysis, NMR and IR spectroscopy.

One-pot multicomponent synthesis of substituted 5,7-dihydro-1,6-naphthyridines and 5,6,7,8-tetrahydroquinolines

Abstract An one-pot approach was developed for the synthesis of substituted 5,7-dihydro-1,6-naphthyridines and 5,6,7,8-tetrahydroquinolines with moderate to good yields. This pathway is a modified two-step synthesis of Kröhnke pyridine and involves a four-component tandem reaction of N-phenacylpyridinium bromide, aromatic aldehydes, substituted or nitrogen-containing cyclic ketones and a nitrogen source. This multi-component reaction is performed using microwave irradiation heating of the reaction substrates under an environment of NH4OAc/HOAc.

New Substituted Indolizines by 1,3-Dipolar Cycloaddition Reactions I. 7-tert-Butylindolizines

The new indolizine derivatives 6a-h containing a tert-butyl group grafted on the pyridinic ring were obtained by reaction of N-phenacylpyridinium bromides 3 with ethyl propiolate as acetylenic dipolarophile in medium of 1,2-epoxybutane at reflux. Structural proof for the compounds was provided by elemental analysis and NMR spectroscopy, including COSY and HETCOR experiments.

N-Phenacylpyridinium Bromides as Acid Corrosion Inhibitors

The inhibiting effect of N-phenacylpyridinium bromides with the amide group in the pyridine ring on corrosion of carbon steel in 3 M sulfuric acid is studied. A relationship between the nature of substituents at the amide group and the corrosion-protective properties of the compounds studied is revealed. Compounds demonstrating high protection efficiency in acid solutions at elevated temperatures are found.

Novel synthetic routes to nitrogen-bridged tricyclic derivatives of pyrrolo[2,1,5-cd]indolizine and pyrrolo[2,1,5-de]quinolizine derived from 2-acyl-N-(acylmethyl)pyridinium halides

Novel synthetic routes to nitrogen-bridged derivatives of pyrrolo[2,1,5-cd]indolizine and pyrrolo[2,1,5-de]quinolizine were developed starting from 2-acyl-N-(acylmethyl)pyridinium halides. Thus, 2-benzoyl-N-phenacylpyridinium bromide (1) afforded 3,4-diphenylpyrrolo[2,1,5-cd]indolizines (4) via 1,3-dipolar cycloaddition, to yield 3,5-dibenzoylindolizines (3), followed by intramolecular McMurry coupling. Similarly, 2-(1,3-dioxolan-2-yl)-N-phenacylpyridinium bromide (5) gave 3-phenylpyrrolo[2,1,5-cd]indolizine (7) together with the unexpected product 3-phenyl-4-hydroxypyrrolo[2,1,5-cd]indolizines (8). However, 2-acetyl-N-phenacylpyridinium bromide (13) or 2-benzoyl-N-acetonylpyridinium bromide (16) underwent a tandem reaction of aldol condensation and 1,3-dipolar cycloaddition to form 3-phenyl-5H-pyrrolo[2,1,5-de]quinolizin-5-ones (15) or 5-phenyl-3H-pyrrolo[2,1,5-de]quinolizin-3-ones (17) in a single step. These novel procedures are general and can be carried out under convenient conditions.

Substituted indolizines and indenoindolizines

Indolizines, indeno[1,2-g]indolizine, and indeno[1,2-e]indolizine containing benzoyl and carbomethoxy groups in the five-membered ring were obtained, respectively, by condensation of ring-substituted N-phenacylpyridinium bromide and the analogous 3-methyl-2-azafluorenium bromide quaternary salts, as well as 4-azafluorenium bromide, with dimethyl acetylenedicarboxylate in the presence of triethylamine. A substituted indeno[2,3-f]indolizine was obtained from the analogous quaternary 9-oxo-3-methyl-2-azafluorenium quaternary salt by the Chichibabin method. 9-Oxo-3-methyl-2-azafluorenium dibenzoylmethylid and 5-oxo-2-phenyl-3-benzoylindeno[2,3-f]indolizine were also synthesized. Deuterium exchange in 9-oxo-3-methyl-2-phenacyl-2-azafluorenium bromide was studied by means of PMR spectroscopy, and information regarding the protonation of the substituted indeno[2,3-f]indolizines was obtained.

Linear free energy realtionships for carbon-13 chemical shifts in N-phenacylpyridinium bromides

Quantitative relationships between the carbon-13 chemical shift of the carbonyl and methylene carbon atoms of N-phenacylpyridinium bromides and σ+ values for 3- and 4-substituents on the pyridine ring have been found.

Reactions of pyridinium and isoquinolinium phenacylides with nucleophiles

The hydrolysis, alcoholysis, and hydrazinolysis of N-phenacylpyridinium bromide lead to the corresponding benzoic acid derivatives. In addition, 3,6-diphenylpyridazine is formed during hydrazinolysis. The hydrolysis and alcoholysis of N-phenacylisoquinolinium bromide lead to its dimerization, whereas hydrazinolysis gives a triazinoisoquinoline derivative.