Tandem Hydroformylation/Reductive Amination of 3‐Allyl‐2‐methylquinazolin‐4(3H)‐one

The 3‐allyl‐2‐methylquinazolin‐4(3H)‐one ( 1 ), a model functionalized terminal olefin, was submitted to hydroformylation and reductive amination under optimized reaction conditions. The catalytic carbonylation of 1 in the presence of Rh catalysts complexed with phosphorus ligands under different reaction conditions afforded a mixture of 2‐methyl‐4‐oxoquinazoline‐3(4H)‐butanal ( 2 ) and α,2‐dimethyl‐4‐oxoquinazoline‐3(4H)‐propanal ( 3 ) as products of ‘linear’ and ‘branched’ hydroformylation, respectively (Scheme 2). The hydroaminomethylation of quinazolinone 1 with arylhydrazine derivatives gave the expected mixture of [(arylhydrazinyl)alkyl]quinazolinones 5 and 6 , besides a small amount of 2 and 3 (Scheme 3). The tandem hydroformylation/reductive amination reaction of 1 with different amines gave the quinazolinone derivatives 7 – 10 . Compound 10 was used to prepare the chalcones 11a and 11b and pyrazoloquinazolinones 12a and 12b (Scheme 4).     

One‐Pot,Three‐Component Condensation of Aldehydes, 2‐Naphthol and 1,3‐Dicarbonyl Compounds

A practical and efficient procedure for the one‐pot multicomponent couping of aryl aldehydes, 2‐naphthol and cyclic 1,3‐dicarbonyl compounds using perchloric acid adsorbed on silica gel (HClO₄‐SiO₂) as a highly efficient, inexpensive, convenient, reusable heterogeneous catalyst under solvent‐free conditions has been developed. Various biologically important 12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one derivatives have been efficiently synthesized in high to excellent yields. The present approach offers several advantages such as shorter reaction times, simple work‐up, excellent yields, low cost, and mild reaction conditions. Furthermore, the catalyst can be recovered simply and reused without appreciable loss of its catalytic activity.     

Palladium(0)/PAr3‐Catalyzed Intermolecular Amination of C(sp3)H Bonds: Synthesis of β‐Amino Acids

An intermolecular C(sp³)? H amination using a Pd⁰/PAr₃ catalyst was developed. The reaction begins with oxidative addition of R₂N? OBz to a Pd⁰/PAr₃ catalyst and subsequent cleavage of a C(sp³)? H bond by the generated Pd? NR₂ intermediate. The catalytic cycle proceeds without the need for external oxidants in a similar manner to the extensively studied palladium(0)‐catalyzed C? H arylation reactions. The electron‐deficient triarylphosphine ligand is crucial for this C(sp³)? H amination reaction to occur.     

A novel hydrophobic copper complex supported on γ‐Fe2O3 as a magnetically heterogeneous catalyst for one‐pot three‐component synthesis of α‐aminophosphonates

A novel hydrophobic copper complex supported on γ‐Fe₂O₃ is synthesized and characterized by different methods such as FT‐IR, XRD, TEM, SEM, TGA, VSM, ICP and CHN analysis. It was used as a magnetically recyclable heterogeneous catalyst for the efficient synthesis of α‐aminophosphonates via a one‐pot three‐component reaction under solvent‐free conditions. The present catalytic system worked extremely well for the synthesis of α‐aminophosphonates even up to five subsequent trails without significant loss of its catalytic activity or copper leaching. The TEM image and FT‐IR spectrum of the catalyst after five times recovery showed that the structure of the catalyst was stable under the reaction conditions with no change being observed. The strong magnetic properties of the reused catalyst were revealed by complete and easy attraction using an external magnet and also by VSM curve. This work represents the first and unique example of a hydrophobic copper complex for catalysis in water generating reactions.     

Chemoselective Amination of Propargylic C(sp3)H Bonds by Cobalt(II)‐Based Metalloradical Catalysis

Highly chemoselective intramolecular amination of propargylic C(sp³)? H bonds has been demonstrated for N‐bishomopropargylic sulfamoyl azides through cobalt(II)‐based metalloradical catalysis. Supported by D_2h‐symmetric amidoporphyrin ligand 3,5‐Di^tBu‐IbuPhyrin, the cobalt(II)‐catalyzed C? H amination proceeds effectively under neutral and nonoxidative conditions without the need of any additives, and generates N₂ as the only byproduct. The metalloradical amination is suitable for both secondary and tertiary propargylic C? H substrates with an unusually high degree of functional‐group tolerance, thus providing a direct method for high‐yielding synthesis of functionalized propargylamine derivatives.     

Piperazine‐functionalized nickel ferrite nanoparticles as efficient and reusable catalysts for the solvent‐free synthesis of 2‐amino‐4H‐chromenes

Piperazine‐functionalized nickel ferrite (NiFe₂O₄) nanoparticles were synthesized as recoverable heterogeneous base catalysts using a routine method. The synthesized materials were characterized using various spectroscopic techniques such as infrared, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray, thermogravimetry analysis, and vibrating sample magnetometry. Catalytic efficiency was investigated in the synthesis of 2‐amino‐4H‐chromene derivatives via a one‐pot three component reaction of aldehyde and malononitrile with β or α‐naphthol/5‐methyle resorcinol under solvent‐free conditions with good to high yields. This method is operationally simple and has several advantages such as good to high yield, short reaction times, solvent‐free conditions, and easy synthesis. Moreover, the catalyst was recovered easily using an external magnet and reused three times without distinctive loss in catalytic activity.     

Aminopropylated PEG as a novel,eco‐friendly and biodegradable basic catalyst for bis‐Michael addition to α,β‐unsaturated ketones under solvent‐free conditions

A solvent‐free and highly efficient protocol has been developed for the synthesis of novel bis‐Michael addition products ( 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l , 3m , 3n , 3o ) using aminopropylated PEG‐6000 (NH₂‐PEG) as a biodegradable and recyclable catalyst in excellent yields under solvent‐free conditions. Other remarkable features of this environmentally benign protocol are shorter reaction time, tolerance of a wide range of C―H‐activated acids, high yield of products, and simple experimental and work‐up procedure as compared to conventional methods. The NH₂‐PEG catalyst is characterized by using FT‐IR, powder XRD and scanning electron microscopy–energy dispersion X‐ray spectrometric analyses. The catalyst can be recycled several times without significant loss of its catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Merging Aerobic Oxidation and Enamine Catalysis in the Asymmetric α‐Amination of β‐Ketocarbonyls Using N‐Hydroxycarbamates as Nitrogen Sources

We describe herein an unprecedented asymmetric α‐amination of β‐ketocarbonyls under aerobic conditions. The process is enabled by a simple chiral primary amine through the coupling of a catalytic enamine ester intermediate and a nitrosocarbonyl (generated in situ) derived from N‐hydroxycarbamate. The reaction features high chemoselectivity and excellent enantioselectivity for a broad range of substrates.     

One‐Pot N‐Deprotection and Catalytic Intramolecular Asymmetric Reductive Amination for the Synthesis of Tetrahydroisoquinolines

A one‐pot N‐Boc deprotection and catalytic intramolecular reductive amination protocol for the preparation of enantiomerically pure tetrahydroisoquinoline alkaloids is described. The iodine‐bridged dimeric iridium complexes displayed superb stereoselectivity to give tetrahydroisoquinolines, including several key pharmaceutical drug intermediates, in excellent yields under mild reaction conditions. Three additives played important roles in this reaction: Titanium(IV) isopropoxide and molecular iodine accelerated the transformation of the intermediate imine to the tetrahydroisoquinoline product; p ‐toluenesulfonic acid contributed to the stereocontrol.     

Propylene Dimerization by（η^5—C9H7）2 Nickel（Ⅱ）Catalytic System

The catalytic performance of Ni(η^5-Ind)2 complex in the dimerization of propylene was studied in combimation with an organoaluminum co-catalyst,eventually in the presence of a phosphine ligand.The effects of the type of aluminum co-catalyst and its relative amount,the nature of phosphine ligand and P/Ni ratio as well as the reaction temperature were examined.The results indicated that the nickel precatalyst exhibited high productivity for the propylene dimerization together with organoaluminum.It was likely to strongly modify the reactivity in the catalytic sytem when using phosphine ligand as additives,especially at the reaction temperature below 0℃.The catalytic system based on Ni(η^5-Ind)2 complex displaed an extremely high productivity(TOF up to 16900h^-1)and a good regioselectivity to 2,3-dimethylbutenes (2,3-DMB) in dimers(66.4%)under proper reaction parameters.     

A practical synthesis of 2‐aminobenzothiazoles via copper(I)‐catalyzed tandem reaction of 2‐iodoanilines with isothiocyanates in ionic liquids

A copper(I)‐catalyzed tandem reaction of 2‐iodoanilines with isothiocyanates was achieved in hydrophobic [bmim][PF₆] ionic liquid under mild conditions, generating a variety of 2‐aminobenzothiazoles in good to excellent yields. The tandem reaction that was carried out in [bmim][PF₆] has some obvious advantages such as accelerated reaction rate and increased yield as compared with the reaction run in volatile solvents such as toluene. Furthermore, the CuI/1,10‐phenanthroline catalytic system can be reused up to eight times without loss of activity and efficiency. Copyright © 2016 John Wiley & Sons, Ltd.     

Three‐component solventless Strecker synthesis of α‐aminonitriles catalysed by a renewable sulfonated nanoporous carbon catalyst (CMK‐5‐SO3H)

The one‐pot three‐component synthesis of a variety of α‐aminonitriles has been studied using a catalytic amount of a sulfonic acid‐functionalized ordered nanoporous carbon catalyst, CMK‐5‐SO₃H, at room temperature under solvent‐free reaction conditions. The heterogeneous catalyst could be readily isolated from the reaction mixture and reused at least ten times without significant loss in activity. A clean, rapid and simple method for the preparation of α‐aminonitriles using the recoverable CMK‐5‐SO3H catalyst is described.     

Nanostructured Pyrophosphate Na2PdP2O7‐Catalyzed Suzuki‐Miyaura Cross‐Coupling Under Microwave Irradiation

Nanostructured palladium pyrophosphate (Na₂PdP₂O₇) catalyst was synthesized and well characterized by using different techniques (TGA, XRD, SEM, TEM....). This nanocatalyst exhibited excellent catalytic activity in the synthesis of biaryl compounds via Suzuki‐Miyaura cross‐coupling to produce their corresponding products in good to excellent yields under mild conditions. The catalyst is recyclable and was recycled for four runs for the reaction of 4‐bromoacetophenone with phenylboronic acid without appreciable loss of its catalytic activity.     

Synthesis of 1‐H‐1,5‐benzodiazepines derivatives using SiO2/ZnCl2

A general and easy method for the synthesis of several 1‐H‐1,5‐benzodiazepines using SiO₂/ZnCl₂ under solvent‐free conditions is described. This efficient and improved method furnishes selectively and in good yields the corresponding 1‐H‐1,5‐benzodiazepines derivatives starting from o‐phenylenediamine and cyclic or acyclic ketones. The catalytic system was reused up four times, and the use of focused microwaves accelerates the reaction. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:180–185, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20674     

An Efficient One‐Pot Synthesis of 7,7‐Dimethyl‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐4‐aryl‐7,8‐dihydroquinolin‐5(6H)‐one Derivatives Using Chitosan–SO3H as Biodegradable Organocatalyst

Chitosan sulfonic acid (CS–SO₃H), a biodegradable green catalyst, was found to be an impressive system for one‐pot four‐component reaction of different aromatic aldehydes, 3‐acetylcoumarin, dimedone, and ammonium acetate leading to 7,7‐dimethyl‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐4‐aryl‐7,8‐dihydroquinolin‐5(6H)‐one under solvent‐free condition. This methodology produces diverse superiorities such as operational simplicity, short reaction time, and high yield. Further, the catalyst can be reused for four times without any noticeable decrease in the catalytic activity.     

Highly Efficient Synthesis of Heterocyclic and Alicyclic β2‐Amino Acid Derivatives by Catalytic Asymmetric Hydrogenation

A valuable class of new heterocyclic and alicyclic prochiral α‐aminomethylacrylates has been conveniently synthesized through a three‐step transformation involving a Baylis–Hillman reaction, O‐acetylation, and a subsequent allylic amination. The corresponding novel β²‐amino acid derivatives were prepared with excellent enantioselectivities and high yields by catalytic asymmetric hydrogenation using the catalyst rhodium(Et‐Duphos) (Et‐Duphos=2′,5′,2′′,5′′‐tetraethyl‐1,2‐bis(phospholanyl)benzene)) under mild reaction conditions (up to 99 % ee and S/C=1000). The influence of the substrate on the enantioselectivity and reactivity is investigated, and the most suitable substrate configuration for the highly efficient enantioselective hydrogenation of β‐substituted α‐aminomethylacrylates under the Rh–Duphos system is reported. The current protocol provides a very practical, facile, and scalable method for the preparation of heterocyclic and alicyclic β²‐amino acids and their derivatives.     

Cu (II)‐β‐cyclodextrin complex stabilized on magnetic nanoparticles: A retrievable hybrid promoter for green synthesis of spiropyrans

The magnetic core of manganese ferrite (MnFe₂O₄) nanoparticles has a significant stability in comparison with ferrite (Fe₃O₄) nanoparticles. The unique supramolecular properties of β‐cyclodextrin (β‐CD), such as hydrophobic cavity, hydrophilic exterior and ‐OH functional groups, make it a good candidate for functionalization and catalytic application. So, a surface‐modified magnetic solid support with the Cu (II)‐β‐CD complex was prepared. The structure of nanoparticles was characterized by Fourier transform‐infrared spectroscopy, X‐ray powder diffraction, thermogravimetric analysis, vibrating‐sample magnetometry, inductively coupled plasma‐optical emission spectrometry and scanning electron microscope analyses. The catalytic activity of these nanoparticles was investigated in the synthesis of spiropyrans and high yields of desired products obtained under green media. Some advantages of this novel catalyst for this reaction are high yields, short reaction times, green solvent and conditions, easy workup procedure, negligible copper leaching, reusability without a significant diminish in catalytic efficiency, and simple separation of nanocatalyst by using an external magnet alongside the environmental compatibility and sustainability.     

Electron Transfer‐Initiated Epoxidation and Isomerization Chain Reactions of β‐Caryophyllene

The abundant sesquiterpene β‐caryophyllene can be epoxidized by molecular oxygen in the absence of any catalyst. In polar aprotic solvents, the reaction proceeds smoothly with epoxide selectivities exceeding 70 %. A mechanistic study has been performed and the possible involvement of free radical, spin inversion, and electron transfer mechanisms is evaluated using experimental and computational methods. The experimental data—including a detailed reaction product analysis, studies on reaction parameters, solvent effects, additives and an electrochemical investigation—all support that the spontaneous epoxidation of β‐caryophyllene constitutes a rare case of unsensitized electron transfer from an olefin to triplet oxygen under mild conditions (80 °C, 1 bar O₂). As initiation of the oxygenation reaction, the formation of a caryophyllene‐derived radical cation via electron transfer is proposed. This radical cation reacts with triplet oxygen to a dioxetane via a chain mechanism with chain lengths exceeding 100 under optimized conditions. The dioxetane then acts as an in situ‐formed epoxidizing agent. Under nitrogen atmosphere, the presence of a one‐electron acceptor leads to the selective isomerization of β‐caryophyllene to isocaryophyllene. Observations indicate that this isomerization reaction is a novel and elegant synthetic pathway to isocaryophyllene.     

Clean Procedure for the Synthesis of Α‐Aminophosphonates Catalyzed by Choline‐Based Ionic Liquid

A sulfated choline‐based ionic liquid [Ch‐OSO₃H] was prepared and used as a novel catalyst for the synthesis of α‐aminophosphonates via a one‐pot three‐component reaction with aldehydes, amines, and triethyl phosphite/diethyl phosphite at room temperature under solvent‐free conditions or in aqueous media. The reaction was completed in short times and products could be simply separated from the reaction mixture in good to excellent yields. The catalyst could be recycled and reused for several times without noticeably reducing catalytic activity.     

Novel nano molten salt tetra‐2,3‐pyridiniumporphyrazinato‐oxo‐vanadium tricyanomethanide as a vanadium surface‐free phthalocyanine catalyst: Application to Strecker synthesis of α‐aminonitrile derivatives

Efficient and recyclable novel nano tetra‐2,3‐pyridiniumporphyrazinato‐oxo‐vanadium tricyanomethanide, {[VO(TPPA)][C(CN)₃]₄}, as a vanadium surface‐free phthalocyanine‐based molten salt catalyst was successfully designed, produced and used for the Strecker synthesis of α‐aminonitrile derivatives through a one‐pot three‐component reaction between aromatic aldehydes, trimethylsilyl cyanide and aniline derivatives under neat conditions at 50 °C. This catalyst was well characterized using Fourier transform infrared, UV–visible, X‐ray photoelectron and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, scanning and high‐resolution transmission electron microscopies, inductively coupled plasma mass spectrometry and thermogravimetric analysis. The catalyst can be simply recovered and reused several times without significant loss of catalytic activity.