Triton B catalyzed three‐component,one‐pot synthesis of 2‐amino‐2‐chromenes at ambient temperature

A one‐pot, three‐component synthesis of 2‐amino‐2‐chromenes is described at ambient temperature by the reaction of an aldehyde and malononitrile or ethyl cyanoacetate with α‐naphthol or β‐naphthol in ethanol in presence of a catalytic amount of Triton B. J. Heterocyclic Chem., (2011).     

A Novel and Efficient Catalyst to One‐Pot Synthesis of 2‐Amino‐4H‐Chromenes by Methanesulfonic Acid

Methanesulfonic acid efficiently catalyzes the one‐pot, three component reaction of an aromatic aldehyde, malonitrile and α or β‐naphthol to yield 2‐amino‐4H‐chromenes in very good yields.     

Triflic Acid Mediated Cascade Cyclization of Aryldiynes for the Synthesis of Indeno[1,2‐c]chromenes: Application to Dye‐Sensitized Solar Cells

A new triflic acid (TfOH)‐mediated cascade cyclization of ortho‐anisole‐substituted aryldiynes is described for the construction of indeno[1,2‐c]chromenes. The cascade cyclization proceeds through an unusual TfOH‐induced alkyne‐alkyne cyclization followed by nucleophilic attack of the methoxy group on the benzylidene cation, which is completely different to the cyclization of ortho‐aniline‐ or ortho‐thioanisole‐substituted aryldiynes. A new class of organic dyes with the indeno[1,2‐c]chromene framework as both donor and π‐linker were synthesized. These compounds exhibit high photovoltaic performances in dye‐ sensitized solar cells (DSCs).     

Reaction between ortho‐Hydroxy Aromatic Aldehydes and Dialkyl Acetylenedicarboxylates in the Presence of Silica Gel in Solvent‐Free Conditions

A two‐component condensation reaction between an ortho‐hydroxy aromatic aldehyde and an electron‐poor acetylenic ester efficiently provides fully substituted electron‐poor aryl vinyl ethers and chromenes in a one‐pot reaction in the presence of silica‐gel in solvent‐free conditions.     

Synthesis of hybrid perillyl-4H-pyrans. Cytotoxicity evaluation against hepatocellular carcinoma HepG2/C3A cell line

A series of 15 new hybrid perillyl-4H-pyrans compounds was straightforwardly synthesized by a strategy combining the multicomponent reaction and the copper-catalyzed alkyne-azide cycloaddition (CuAAC). The 2-amino-4H-pyrans-3-carbonitrile containing the alkyne moiety was prepared via multicomponent reaction between 1,3-dicarbonyl, a propargyloxy aromatic aldehyde and malononitrile or ethyl α-cyanoacetate. The alkyne derivative was sequentially reacted with the perillyl azide component through the copper-catalyzed [3+2] Huisgen cycloaddition reaction. The antiproliferative activity of hybrid compounds were evaluated against the human hepatoma HepG2/C3A cell line.     

A one‐pot green synthesis of 2‐amino‐4H‐benzo[h]chromenes catalyzed by a dioxomolybdenum Schiff base complex supported on magnetic nanoparticles as an efficient and recyclable nanocatalyst

In this work, catalytic performance of a molybdenum Schiff base complex‐supported magnetic support as a nanocatalyst was evaluated for the preparation of 2‐amino‐4H‐benzo[h]chromenes through one‐pot, three component reactions of 1‐naphthol, various aldehydes, and malononitrile under solvent‐free conditions. A promising greener and eco‐friendly method with a short reaction time, high yield of products, and simple work‐up procedure was achieved. The nanocatalyst could be easily separated and regenerated from reaction media by an external magnet and reused at least seven consecutive times with small drops in its catalytic performance.     

One‐pot Three‐component Route for the Synthesis of Functionalized 4H‐chromenes Catalyzed by ZrOCl2·8H2O in Water

An efficient method for the synthesis of functionalized 4H‐chromenes via a one‐pot three‐component condensation reaction of a 2‐hydroxybenzaldehyde with an active methylene compound and a carbon‐based nucleophile in the presence of a catalytic amount of ZrOCl₂·8H₂O in water under thermal condition has been described. High yields, simple work‐up procedure, performing reactions in water and synthesis of complex molecules with a one‐pot procedure are the main advantages of this procedure. In addition, the structure of the product from the condensation of salicylaldehyde, 2‐naphthol, and dimedone was confirmed by X‐ray crystallography.     

DBU: a highly efficient catalyst for one-pot synthesis of substituted 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-b]pyranes, 2-amino-4H-benzo[h]chromenes and 2-amino-4H benzo[g]chromenes in aqueous medium

We have reported DBU catalyzed one-pot synthesis of 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-b]pyranes, 2-amino-4H-benzo[h]chromenes and 2-amino-4H-benzo[g]chromenes from aldehydes, active methylene compounds malononitrile/ethyl cyanocacetate, and 4-hydroxycoumarin/4-hydroxy-6-methylpyrone/1-naphthol/2-hydroxynaphthalene-1,4-dione in water under reflux. The attractive features of this process are mild reaction conditions, reusability of the reaction media, short reaction times, easy isolation of products, and excellent yields.     

Convenient Method for Synthesis of Substituted 2‐Amino‐2‐chromenes

Some substituted 2‐amino‐2‐chromenes were synthesized by the reaction of arylidenemalononitriles with 1‐naphthol or 2‐naphthol in the presence of sodium hydroxide as catalyst under solvent‐free condition.     

Triethanolamine‐catalyzed expeditious and greener synthesis of 2‐amino‐4H‐chromenes

Triethanolamine (TEOA), an inexpensive and eco‐friendly base, was used to efficiently catalyze the three‐component condensation reaction of heterocyclic/aromatic aldehyde, (α/β)‐naphthol, and malononitrile in water to give the corresponding substituted 2‐amino‐4H‐chromene derivatives with excellent yields.     

Novel and efficient catalysts for the one-pot synthesis of 3,4-dihydropyrano[c]chromene derivatives in aqueous media

Diammonium hydrogen phosphate, (NH₄)₂HPO₄(DAHP), efficiently catalyzes the one-pot, three-component reaction of an aromatic aldehyde, malononitrile and 4-hydroxycoumarin in aqueous media under mild conditions at room temperature, to afford the corresponding dihydropyrano[c]chromenes in high yields. (S)-Proline has also been used as another neutral catalyst for this reaction at reflux.     

Practical and Green Protocol for the Synthesis of Substituted 4H‐Chromenes Using Room Temperature Ionic Liquid Choline Chloride–Urea

An efficient and convenient synthesis of substituted 4H‐chromenes is described using room temperature ionic liquid (RTIL) choline chloride–urea in one pot under solvent free conditions. Three‐component Knoevenagel condensation of an aromatic aldehyde, with an active methylene compound, and a cyclohexane dione is reported. This new approach has advantage of excellent yields (82–96%), clean reaction, and short reaction time (15–30 min) at room temperature.     

Highly Efficient One‐Pot Three‐Component Synthesis and Antimicrobial Activity of 2‐Amino‐4H‐chromene Derivatives

A remarkably efficient three‐component reaction to synthesize 2‐amino‐4H‐chromenes derivatives from malononitrile, various aromatic aldehydes, and orcinol was described at room temperature in CH₂Cl₂ in the presence of catalytic amount of triethylamine. In a facile one‐pot procedure, excellent yields of products were achieved in less than 1 h. Some of the synthesized 2‐amino‐4H‐chromenes derivatives demonstrated potent antibacterial activities against Gram‐positive bacteria including Staphylococcus aureus and Bacillus anthracis, indicated by disk method, minimum inhibitory concentration, and minimum bactericidal concentration approaches. However, none of the tested compounds expressed any antibacterial activities against Enterococcus faecalis and Gram‐negative bacteria.     

A Convenient Fluorescent Method to Simultaneously Determine the Enantiomeric Composition and Concentration of Functional Chiral Amines

A 1,1′‐bi‐2‐naphthol (BINOL)‐based chiral aldehyde in combination with Zn^II shows a highly enantioselective fluorescent response toward functional chiral amines at λ>500 nm. However, the combination of salicylaldehyde and Zn^II gives the same fluorescent enhancement for both enantiomers of a functional chiral amine at λ=447 nm. By using the fluorescent responses of the combination of the BINOL‐based chiral aldehyde, salicylaldehyde and Zn^II at the two emission wavelengths, both the concentration and enantiomeric composition of functional chiral amines such as amino alcohols, diamines, and amino acids can be simultaneously determined by a single fluorescent measurement. This work provides a simple and convenient method for chiral assay.     

Polypyrrole/Fe3O4/CNT as a recyclable and highly efficient catalyst for one‐pot three‐component synthesis of pyran derivatives

Polypyrrole (PPY)/Fe₃O₄/CNT has been synthesized and characterized by FT‐IR, TEM and SEM techniques and its catalytic activity has been evaluated in the synthesis of several series of pyran derivatives. Tetrahydrobenzo[b]pyranes, 4H‐pyran‐3‐carboxylates, 4H,5H‐pyrano[3,2‐c]chromenes and dihydropyrano[2,3‐c]pyrazoles have been successfully prepared from one‐pot three‐component condensation of aldehyde, malononitrile and active methylene‐containing compounds (dimedone /ethyl acetoacetate/4‐hydroxycoumarin/3‐methyl‐2‐pyrazoline‐5‐one) using PPY/Fe₃O₄/CNT as a new and reusable heterogeneous catalyst. The present method offer several advantages such as; high yields of products, short reaction times, easy work‐up procedure and easy separation of the catalyst from the reaction mixture due to its magnetic character. Furthermore, chemoselective synthesis of bis‐benzo[b]pyran from terephthalaldehyde can be achieved by this method.     

Preparation and orthogonal postmodification of dual‐clickable polymer precursors bearing both aldehyde and alkyne groups

A new styrenic monomer 2‐propargyloxy‐5‐vinylbenzaldehyde (PVB) containing both aldehyde and alkyne reactive groups was designed for the synthesis and subsequent orthogonal postfunctionalization of dual‐clickable polymer precursor. Reversible addition‐fragmentation chain transfer polymerization of PVB afforded a structurally well‐defined polymer poly(2‐propargyloxy‐5‐vinylbenzaldehyde) (PPVB) bearing alkyne and aldehyde functionalities that are reactive towards azide ‐ and aminooxy‐containing molecules, respectively. Therefore, the resulting PPVB can be served as a dual‐clickable polymer scaffold for construction of multiple functional polymers via orthogonal alkyne–azide and aldehyde–aminooxy click reactions. Postpolymerization modification of PPVB sequentially with aminooxy‐terminated poly(ethylene oxide)s (H₂NO‐PEO) and azide‐functionalized imidazolium‐type ionic liquid (N₃‐IL·TFSI, having bis(trifluoromethane)sulfonamide, TFSI, counter‐anion) yielded an interesting multicomponent graft polymer PPVB‐g‐(PEO‐and‐IL·TFSI). After anion exchange of hydrophobic TFSI counter‐anion by bromide (Br) anion, the resulting graft copolymer PPVB‐g‐(PEO‐and‐IL·Br) becomes soluble in water, and its imidazolium units can capture negatively charged tetraphenylethylene disulfonate derivative (TPE‐2 ) guest molecule via electrostatic complexation to form in situ self‐assembled fluorescent nanoaggregates with colloidal stability imparted by hydrophilic PEO chains. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2650–2656     

Synthesis of 5-Amino-9-benzyl-6-formyl-4-methoxy-2-pivaloylamino-7,8-dihydropyrimido[4,5-b]azepine. A potentially useful intermediate towards the synthesis of pyrimidoazepine based folic acid derivatives

Synthesis of the title compound is described via an intramolecular 1,3-dipolar cycloaddition reaction between the pyrimidine nitrile oxide 24 and an alkyne dipolarophile tethered to the 6-position of the pyrimidine ring. The resulting isoxazolopyrimidoazepine cycloadduct 25 was treated with molybdenum hexacarbonyl to provide the titled enamino aldehyde 26 .     

A Sequential Homologation of Alkynes and Aldehydes for Chain Elongation with Optional 13C‐Labeling

Terminal alkynes (RCCH) are homologated by a sequence of ruthenium‐catalyzed anti‐Markovnikov hydration of alkyne to aldehyde (RCH₂CHO), followed by Bestmann–Ohira alkynylation of aldehyde to chain‐elongated alkyne (RCH₂CCH). Inverting the sequence by starting from aldehyde brings about the reciprocal homologation of aldehydes instead. The use of ¹³C‐labeled Bestmann–Ohira reagent (dimethyl ((1‐¹³C)‐1‐diazo‐2‐oxopropyl)phosphonate) for alkynylation provides straightforward access to singly or, through additional homologation, multiply ¹³C‐labeled alkynes. The labeled alkynes serve as synthetic platform for accessing a multitude of specifically ¹³C‐labeled products. Terminal alkynes with one or two ¹³C‐labels in the alkyne unit have been submitted to alkyne–azide click reactions; the copper‐catalyzed version (CuAAC) was found to display a regioselectivity of >50 000:1 for the 1,4‐ over the 1,5‐triazine isomer, as shown analytically by ¹³C NMR spectroscopy.     

Four cytotoxic N4‐substituted thiosemicarbazones derived from 2‐hydroxynaphthalene‐1‐carboxaldehyde

The X‐ray crystal structures are reported of four novel and potentially O,N,S‐tridentate donor ligands that demonstrate antitumour activity. These ligands are 1‐[(4‐methyl­thio­semicarbazono)methyl]‐2‐naphthol, C₁₃H₁₃N₃OS, (III), 1‐[(4‐ethylthio­semicarbazono)­methyl]‐2‐naphthol, C₁₄H₁₅N₃OS, (IV), 1‐[(4‐phenyl­thio­semicarbazono)­methyl]‐2‐naphthol, C₁₈H₁₅N₃OS, (V), and 1‐[(4,4‐di­methyl­thio­semicarbazono)­methyl]‐2‐naphthol di­methyl sulfoxide solvate, C₁₄H₁₅N₃OS·C₂H₆OS, (VI). These chelators are N4‐substituted thio­semicarbazones, each based on the same parent aldehyde, namely 2‐­zhydroxynaphthalene‐1‐carboxaldehyde isonicotinoylhydrazone. Conformational variations within this series are discussed in relation to the optimum conformation for metal‐ion binding.     

Improved molecular weight control in ring‐opening metathesis polymerization reactions in organic and aqueous media using N‐heterocyclic carbene–ruthenium arene/alkyne catalyst systems

A binary catalytic system, RuCl₂(N‐heterocyclic carbene)(p‐cymene)/alkyne, was developed for improved molecular weight control in ring‐opening metathesis polymerization (ROMP) reactions of norbornene derivatives in organic and aqueous media. Monometallic ruthenium arene compounds were activated using aryl and aliphatic terminal alkynes to form highly active metathesis species. The effects of alkyne structure and concentration on the overall catalytic activity were systematically investigated. The catalytic activity of the metathesis active species can be tuned by varying alkyne substituents. Also, the initiation rate of the ROMP reaction can be tuned by increasing the alkyne‐to‐Ru ratio. ROMP polymers with a wide range of molecular weights (91–832 kDa) were isolated in organic media, whereas polymers with a molecular weight range of 110–280 kDa with average particle sizes of 150–250 nm were isolated in aqueous media. Copyright © 2016 John Wiley & Sons, Ltd.