Erlenmeyer Synthesis Research Articles

Silica‐supported Solvent Approaches More Facile than the Conventional for Erlenmeyer Synthesis with Our Pyridinium Salts

The synthesis of pyridinium salts by both conventional/silica‐supported muffle furnace and microwave approaches is described. We have optimized the Erlenmeyer synthesis of azalactone with various concentrations of our synthesized pyridinium salts. Among these, bromide‐containing pyridinium salts showed excellent catalytic activity than the others.

Synthesis and characterization of new green and orange region emitting anthracene based oxazol-5-one dyes

New anthracene oxazol-5-one dyes featuring an extended π-conjugated electron system have been successfully prepared by Erlenmeyer synthesis, structurally characterized and their spectroscopic properties were investigated by UV–vis absorption spectroscopy and fluorescence spectroscopy. The oxazol-5-ones were attached to the 9-position of the anthracene to obtain the desired structures. The dyes are having extended conjugation throughout their structure with oxazol-5-one ring as the chromophore. The spectral properties of the oxazol-5-one ring were monitored with respect to the substituents at the phenyl ring. All of the dyes synthesized show good solubility in common organic solvents. Also in order to establish whether there was any solvent affects the absorption and emission spectra of the compounds were measured in the solvents of acetonitrile, tetrahydrofuran and chloroform which have different polarity. Moreover, their absorption and emission properties were investigated in plasticized PVC film matrix. In comparison to the solution phase, the dyes displayed enhanced fluorescence emission quantum yield values when embedded in poly(vinyl chloride) polymer film. The anthracene based oxazol-5-ones were found to emit in the green portion of the spectrum for 2a and 2b, and in the orange portion of the spectrum for 2c. By attachment of nitro substituent at the para position of the phenyl ring bound to oxazol-5-one core, the fluorescence maxima could be effectively modulated from the green region of the spectra to the orange region. 4-(9-anthralydene)-2-(4-nitrophenyl)oxazol-5-one (2c) exhibits large Stokes shift up to 146 nm presumably due to intramolecular charge transfer.

Microwave-assisted efficient synthesis of azlactones using zeolite NaY as a reusable heterogeneous catalyst

ABSTRACTThe efficient preparation of azlactones in the presence of zeolite NaY has been reported. This heterogeneous catalyst was used for efficient synthesis of azlactone derivatives with Ac2O as a condensing agent under microwave irradiation and solvent-free conditions. The present method offers the advantages of good yields, short reaction time, simple work-up, and catalyst reusability, which makes this method mild and eco-friendly.

Multicomponent synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones (azlactones) using a mechanochemical approach.

BackgroundMechano heterocyclic chemistry (MCH) is a recent quickly growing technique in the synthesis of heterocycles and draws the attention of heterocyclic chemists towards the uses of grindstone technique in a solvent free green efficient synthesis of many heterocyclic systems. On the other hand, multicomponent approach has opened the door for the rapid and efficient one-step procedures to synthesize a wide range of complex targets. Azlactones have been reported to exhibit a wide range of pharmaceutical properties including immune suppressive, anticancer. Antimicrobial, antitumor, anti-inflammatory and antiviral. It also used as useful synthons in the synthesis of several small molecules, including amino acids and peptides.ResultsThe present work describes an efficient one step green synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones (azlactones) via the multi-component synthesis by the mechanochemical grinding of glycine, benzoyl chloride, an aromatic aldehyde and fused sodium acetate in the presence of drops of acetic anhydride. This process is green, simple to handle, step and atom efficient, economical and environmentally friendly, because it does not require a reaction solvent or heating, we introduced the yield economy [YE] as a metric to assess the conversion efficiency of grinding and conventional synthetic reactions of azlactones. The structures of the newly synthesized compounds were elucidated by elemental and spectral analyses.ConclusionIn conclusion, we have developed a simple, efficient and eco-friendly strategy for facile synthesis of azlactones. The key advantages of this strategy, over conventional approach, include its simple, solvent free conditions, as well as its facile work-up, high yield economy and environmental friendliness. It is also successful in achieving three of the green chemistry objectives of a solvent free operation, high atom economy and step efficient. Thus, combining the features of both economic and environmental advantages.Graphical abstractAn efficient one step green synthesis of azlactones via multicomponent synthesis by a mechanochemical grinding.

Triphenylphosphine (PPh3) Catalyzed Erlenmeyer Reaction for Azlactones under Solvent‐free Conditions

This study presents triphenylphosphine catalyzed process for the synthesis of azlactones and their derivatives using hippuric and substituted aromatic aldehydes. The methodology also found to be effective for the synthesis of azlactones from 5‐(2,6‐dichlorophenyl)‐3‐methyl‐1,2‐oxazol‐4‐yl carbonyl amino acetic acid and offers several advantages such as solvent‐free conditions, excellent yields, simple procedure, mild conditions, and reduced environmental consequences.

Microwave-Assisted Erlenmeyer Synthesis of Azlactones Catalyzed by MgO/Al2O3 Under Solvent-Free Conditions

MgO/Al2O3 catalyzes the synthesis of azlactone derivatives from condensation reaction of aldehydes (or ketones) with hippuric acid and acetic anhydride as a dehydrating agent under microwave irradiation. The low toxicity, low cost, ease of handling, and high activity of MgO/Al2O3 make this procedure particularly attractive. Also, this catalyst can be easily recovered by decant and can be reused for this condensation five times in succession without considerable loss of its catalytic activity.

ChemInform Abstract: Microwave‐Assisted Efficient Synthesis of Azlactone Derivatives Using 2‐Aminopyridine‐Functionalized Sphere SiO2 Nanoparticles as a Reusable Heterogeneous Catalyst.

AbstractA new Erlenmeyer synthesis of azlactones is reported which is catalyzed by 2‐aminopyridine supported on nanosized silica. Silica nanoparticles are modified with triethoxysilylpropyl chloride and 2‐aminopyridine attached to the support via covalent linkages.

Microwave-assisted efficient synthesis of azlactone derivatives using 2-aminopyridine-functionalized sphere SiO2 nanoparticles as a reusable heterogeneous catalyst

Abstract In the present work, the highly efficient Erlenmeyer synthesis of azlactones catalyzed by 2-aminopyridine, supported on nano-sphere SiO 2 is reported. First, the silica nanoparticles were modified with triethoxysilylpropyl chloride and then 2-aminopyridine was attached to the support via covalent linkages. This new heterogenized catalyst was used for efficient microwave-assisted synthesis of azlactone derivatives with Ac 2 O as a condensing agent under solvent-free conditions. The present method offers advantages including high yields, short reaction times and simple work-up. Also, the catalyst can be easily recycled and reused several times, which makes this method attractive, economic and environmentally-benign.

Improved Erlenmeyer Synthesis with 5‐Thiazolone and Catalytic Mn(II) Acetate. Crystal Structure Confirmation of the Reaction Stereochemistry

2‐Phenylthiazolin‐5‐one (5, a thioazlactone) condenses with various aldehydes in the presence of the mild base Mn(II) acetate as catalyst in CH2Cl2 solution. This leads to the corresponding Erlenmeyer reaction products (6) in excellent yields in the case of aromatic aldehydes and moderate yields in others. The mildness of the reaction conditions is apparently enabled by the aromaticity of the (putative) intermediate thiazolone anion. The structure and stereochemistry (Z) of the product derived from i‐BuCHO was confirmed by single crystal X‐ray diffraction. This study overcomes key limitations of the classical Erlenmeyer synthesis and also introduces the relatively nontoxic Mn(II) acetate as a reagent in heterocyclic chemistry.

Nanocrystalline titanium dioxide catalyst for the synthesis of azlactones

Titanium dioxide nanoparticles were prepared by a electrochemical reduction method using parameters such as current density, solvent polarity, distance between electrodes, and concentration of stabilizers to control the size of the nanoparticles. The nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and their catalytic performance was tested for the synthesis of a series of 4-aryldiene-2-phenyl-5(4)-oxazolones from the cyclodehydration and condensation of the respective aldehyde, hippuric acid and acetic anhydride. Easy availability, reusability and eco-friendliness were some prominent features of the nanocrystalline titanium dioxide catalyst. Size controlled synthesis of TiO 2 by electrochemical reduction gave nanoparticles for the synthesis of 4-aryldiene-2-phenyl-5(4)-oxazolones. The smaller size catalyst has promising features for the reaction.

Synthesis of the chromophores of fluorescent proteins and their analogs

Members of the green fluorescent protein (GFP) family are widely used in experimental biology as genetically encoded fluorescent tags. Chromophores of GFP-like proteins share a common structural core: 3,5-dihydro-4H-imidazol-4-one. This review covers synthetic approaches to 3,5-dihydro-4H-imidazol-4-ones, substituted at different positions. General, as well as specific methods, represented by single examples are considered. The most popular synthetic route to substituted 3,5-dihydro-4H-imidazol-4-ones includes synthesis of azlactones, followed by transformation into N-acyldehydroaminoacids and, finally, cyclization into target heterocycles. Accordingly, the review is divided into three parts: the first part covers syntheses of azlactones, the second part covers main approaches to N-acyldehydroaminoacids, and in the third part we summarize cyclizations of N-acyldehydroaminoacids, as well as all other approaches to 3,5-dihydro-4H-imidazol-4-ones.

Synthesis and Characterization of Nano Silica Supported Tungstophosphoric Acid: An Efficient, Reusable Heterogeneous Catalyst for the Synthesis of Azlactones

A rapid and scale up protocol for the synthesis of azlactones by the Erlenmeyer method under solvent-free conditions was developed. Tungstophosphoric acid supported on nano-silica, TPA@nano-SiO2 was used as a heterogeneous catalyst for the synthesis of a wide range of azlactone derivatives. The catalyst was characterized by physicochemical measurements. The procedure was simple and permitted the quantitative isolation of products and catalyst under thermal conditions. The recycled catalyst was reused more than 5-times without loss of catalytic activity.

The Zwitterionic Imidazolium Salt: First Used for Synthesis of 4‐Arylidene‐2‐phenyl‐5(4H)‐oxazolones under Solvent‐Free Conditions

The zwitterionic imidazolium salt was prepared and characterized by 1H NMR. It was first used for synthesis of azlactones via Erlenmeyer synthesis from aromatic aldehydes and hippuric acid under solvent‐free conditions. It was found that aldehyde substituents play an important role in these reactions. Better conversions and therefore higher isolated yields were observed when electron‐withdrawing groups (EWG‐) were present in the aromatic aldehyde. Opposite results were shown when electron‐donating groups (EDG‐) were present in the aromatic aldehyde. However, azlactones were obtained in moderate to high yields.

Ammonium metavanadate an efficient catalyst for Erlenmeyer synthesis

Ammonium metavanadate an efficient catalyst for Erlenmeyer synthesis

A green protocol for Erlenmeyer–Plöchl reaction by using iron oxide nanoparticles under ultra sonic irradiation

Azlactones have been prepared via Erlenmeyer synthesis from aromatic aldehydes and hippuric acid using Fe2O3 nanoparticles under ultrasonic irradiation. Short reaction times, easy and quick isolation of the products, and excellent yields are the main advantages of this procedure.

ChemInform Abstract: Novel and Chemoselective One‐Pot Synthesis of 4‐Arylidene‐2‐phenyl‐5(4H)‐oxazolones Starting from Benzyl Alcohols Promoted by [(C14H24N4) 2W10O32]‐[bmim]NO3.

AbstractA new, efficient, and highly chemoselective one‐pot procedure for the synthesis of azlactones via sequential oxidation of benzyl alcohols and subsequent Erlenmeyer—Ploechl reaction is described.

Microwave-assisted efficient synthesis of azlactone derivatives using TsCl/DMF under solvent-free conditions

A simple and efficient procedure for the synthesis of azlactones employing condensation reaction of aromatic aldehydes with hippuric acid has been developed by using the tosyl chloride (TsCl) and dimethylformamide (DMF) system as condensing agent in the absence of solvents under microwave irradiation. The present protocol is operationally simple and offers several advantages such as high yields, short reaction time, and simple workup.

Synthesis of Nine-Membered Azlactones by Palladium-Catalyzed Ring-Expansion of γ-Methylidene-δ-valerolactones with Aziridines

A palladium-catalyzed formal [6 + 3] cyclization of γ-methylidene-δ-valerolactones with aziridines has been developed to produce 1,4-oxazonan-9-ones, a class of nine-membered azlactones that are not easily accessible by existing methods. The products thus obtained can also be further functionalized with ease.

Organic–inorganic hybrid polyoxometalates: Efficient, heterogeneous and reusable catalysts for solvent-free synthesis of azlactones

Two organic–inorganic hybrid polyoxometalates, consist of 1-butyl-3-methylimidazolium salts of (W 10O 32) 4− and (PW 12O 40) 3− polyanions were prepared and characterized by thermal analysis, X-ray diffraction, FT-IR, diffuse reflectance UV–Vis spectroscopic methods and nitrogen absorption–desorption determination (BET). These heterogeneous catalysts were used for synthesis of azlactones by the reaction of aldehydes with hippuric acid and acetic anhydride under solvent-free conditions. These catalysts were reused several times without loss of their activities.

The Erlenmeyer synthesis with a thioazlactone

2-Phenylthiazolin-5-one (2b) was generated in situ and condensed with various aldehydes in CH2Cl2 (r.t./20 min.), to obtain the corresponding 4-alkylidene or arylidene products in good yields (68-81%). The reaction is catalyzed by basic lead acetate, and is equally successful with both aliphatic and aromatic aldehydes. This mild version of the classical Erlenmeyer azlactone synthesis is apparently enabled by the enhanced aromaticity of the thioazlactone anion intermediate.