Direct aldol reactions catalyzed by a heterogeneous guanidinium salt/proline system under solvent-free conditions

The combined activity of (S)-proline and an achiral cocatalyst (a TBD-derived guanidinium salt) allow direct aldol reactions to be carried out with high diastereoselectivity and enantioselectivity under solvent-free conditions with a rather simple reaction setup where stirring is not required.     

An efficient synthesis of benzodiazepinyl phosphonates as clostripain inhibitors via FeCl3 catalyzed four-component reaction

A novel one-pot route for the synthesis of benzodiazepinyl phosphonates (BDPs) has been achieved. FeCl(3) efficiently catalyzed four-component condensation of diamines, acetone and phosphites in the presence of molecular sieves to furnish BDPs as novel chemical entities with good yield. The synthesized BDPs have shown significant protease inhibition activity against clostripain, a disease model for gas gangrene, suggesting that these novel chemical entities could be further explored as cysteine protease inhibitors.     

P2O5/SiO2 as an efficient and recyclable catalyst for N-Acylation of sulfonamides under heterogeneous and solvent-free conditions

A convenient synthetic method for N-acylation of sulfonamides in the presence of P₂O₅/SiO₂ is described. Carboxylic acid anhydrides and carboxylic acid chlorides were used as acylating agents and the reactions were carried out in CH₂Cl₂ or solventfree conditions. The catalyst can be recovered by simple filtration and can be used in the subsequent reactions.     

Aryldiazonium silica sulfates as efficient reagents for Heck-type arylation reactions under mild conditions

An efficient and straightforward procedure for Heck-type arylation reactions was studied using aryldiazonium silica sulfates and olefins in the presence of a catalytic amount of Pd(OAc)₂. These reactions were carried out in water at room temperature without using a base or additional ligands. The use of a non-toxic solvent, a simple and clean work-up, short reaction times, and good yields are advantages of this method.     

Highly efficient three-component (aldehyde-alkyne-amine) coupling reactions catalyzed by a reusable PS-supported NHC-Ag(I) under solvent-free reaction conditions

The development of a highly efficient, polystyrene-supported NHC-Ag(I) catalyst for the three-component coupling reactions of aldehydes, alkynes, and amines (A³-coupling) was described. In the presence of PS-NHC-Ag(I) (2 mol %), the A³-reactions were carried out at room temperature under solvent-free reaction conditions and the corresponding propargylamines were generated in good to excellent yields. Furthermore, the catalyst could be reused at least 12 times without a significant loss of its catalytic activity.     

SiO2/g-C3N4 nanocomposite-catalyzed green synthesis of di-indolyloxindols under mild conditions

In this study, a facile and benign protocol was introduced for the immobilization of SiO₂ nanoparticles onto g-C₃N₄ nanosheets. The corresponding nanocomposite (SiO₂/g-C₃N₄) was characterized by various techniques, including X-ray diffraction, transmission electron microscopy, thermo-gravimetric analysis, and Fourier transform infrared spectra. The activity of a SiO₂/g-C₃N₄ nanocomposite was investigated in C–C bond formation reaction. The Friedel–Crafts 3-indolylation reaction of isatin with indole derivatives was investigated in the presence of a catalytic amount of SiO₂/g-C₃N₄ nanocomposite at ambient temperature in water as a green medium. The results showed that the corresponding products were obtained in good to excellent yields. In addition, the electron-releasing groups in the R¹ position of the indole ring or electron-withdrawing groups on the R⁴ position of isatin gave excellent yields (91–95%). Some advantages of this method include short reaction time, excellent yields, easy work-up, and the use of water as a green solvent.

     

One-pot,four-component synthesis of 2H-indazolo[2,1-b]phthalazine-triones catalyzed by cellulose-SO3H as a reusable heterogeneous and efficient catalyst

A practical and green method for the synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives using cellulose-SO₃H as a solid acidic catalyst for the four-component condensation reaction of hydrazinium hydroxide, phthalic anhydride, dimedone, and aromatic aldehydes under thermal solvent-free conditions is described. Cellulose-SO₃H as a recyclable green chemical compound has been demonstrated as a new catalyst for the synthesis of this class of compounds.     

Highly efficient protection of alcohols as trityl ethers under solvent-free conditions,and recovery catalyzed by reusable nanoporous MCM-41-SO3H

An efficient method was developed for the protection of alcohols as trityl ethers using triphenylmethanol in the presence of nanoporous MCM-41-SO₃H as a heterogeneous catalyst under solvent-free ball-milling at room temperature. Low catalyst loading, high efficiency, reusability are among the advantages of this new solvent-free and environmentally friendly method. The deprotection of the produced trityl ethers was also efficiently achieved using the same catalyst in wet acetonitrile.     

Synthesis of flavanones, azaflavanones, and thioflavanones catalyzed by PMA-SiO2 as a mild, efficient, and reusable catalyst

Abstract  

Cyclization of a variety of chalcones to flavanones catalyzed by 1 mol% phosphomolybdic acid (PMA) supported on silica as a mild, efficient, and reusable catalyst was carried out in high yields. PMA-SiO₂ is an efficient, inexpensive, and green catalyst which gave high conversion yields and could be recycled up to three times without significant loss in activity.     

Wet carbon-based solid acid/potassium permanganate as an efficient heterogeneous reagents for oxidation of alcohols under mild conditions

Wet carbon-based solid acid and potassium permanganate were used as new reagents for oxidation of alcohols to their corresponding aldehydes and ketones in heterogeneous mixtures. The experiments were done moderately at mild condition and high yields in suitable times were obtained.     

1,3-dihalo-5,5-dimethylhydantoin/NaNO2 as an efficient heterogeneous system for the N-nitrosation of N,N-dialkylamines under mild conditions

A combination of 1,3-dihalo-5,5-dimethylhydantoin (X = Br, Cl) and sodium nitrite in the presence of wet SiO₂ was used as an effective nitrosating agent for the nitrosation of N,N-dialkyl amines to their corresponding nitroso derivatives under mild and heterogeneous conditions in good to excellent yields.     

Amberlyst-15: a mild, efficient and reusable heterogeneous catalyst for N-tert-butoxycarbonylation of amines

A mild and versatile method has been developed for the chemoselective N-tert-butoxycarbonylation of amines in the presence of Amberlyst-15 under solvent-free condition. The method is general for the preparation of N-Boc derivatives of aliphatic (acyclic and cyclic) and aromatic amines.     

Stereoselective Pincer-complex catalyzed C-H functionalization of benzyl nitriles under mild conditions. An efficient route to beta-aminonitriles

An efficient palladium pincer-complex catalyzed reaction has been developed for alpha-C-H bond functionalization of benzyl nitriles. The studied coupling reaction with sulfonylimines affords beta-aminonitriles with usually high levels of stereoselectivity. The stereoselectivity of the process is highly dependent on the electronic effects of the ortho substituents of the benzyl moiety. Promising levels of enantiomeric excess are obtained using chiral pincer complexes as catalysts.     

Highly efficient oxidation of alcohols using Oxone as oxidant catalyzed by ruthenium complex under mild reaction conditions

Aromatic and alkyl alcohols were oxidized to the corresponding aldehydes or ketones at room temperature with high conversion and selectivity using Oxone （2KHSOs-KHSO4.K2SO4） as oxidant catalyzed by ruthenium complex Quin-Ru-Quin （where Quin = 8-hydroxyquinoline）. The reaction time is very short and the preparation of complex is simple.     

Facile and efficient method for preparation of schiff bases catalyzed by P2O5/SiO2 under free solvent conditions

A simple and convenient method for the preparation of Schiff bases is developed. In this method, the Schiff base compounds were prepared from the reaction of carbonyl compounds with primary amines. In this reaction, P₂O₅/SiO₂ have catalyzed the Schiff base formation in dry media under solvent‐free conditions. Advantages of this method are use of an inexpensive and efficient catalyst, high yields of products, short reaction times, and simpli‐city of the reaction and workup. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:43–47, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20383     

A convenient synthesis of 2-aminocyclohex-1-ene-1-carboxylic esters by FeCl3/SiO2 nanoparticles as robust and efficient catalyst

A simple and green method has been developed for the synthesis of 2-aminocyclohex-1-ene-1-carboxylic esters through a one-pot three-component condensation reaction of primary amines, ethyl acetoacetate and chalcones using FeCl3/SiO2 nanoparticles in ethanol. This method has several advantages such as high to excellent product yields in short time, using an inexpensive and reusable catalyst and available starting material.     

A simple and efficient one-pot synthesis of Hantzsch 1,4-dihydropyridines using silica sulphuric acid as a heterogeneous and reusable catalyst under solvent-free conditions

A simple, inexpensive and efficient one-pot synthesis of 1,4-dihydropyridine derivatives under solvent-free conditions using silica sulphuric acid (SSA) as a heterogeneous and recyclable catalyst is reported.     

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

In the present work, the highly efficient Erlenmeyer synthesis of azlactones catalyzed by 2- aminopyridine, supported on nano-sphere SiO2 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 Ac2O 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.     

Novel oxidation of toluenes catalyzed by reusable vanadyl(IV) sulfate under mild conditions with molecular oxygen

Efficient oxidation system using reusable vanadyl(IV) sulfate catalyst was established. Toluenes were easily oxidized under molecular oxygen (0.1 MPa) at 100 °C catalyzed by vanadyl(IV) sulfate to afford the corresponding benzoic acids in excellent yields. The recovered catalyst could be reused without loss of activity.