A high yielding, one-pot synthesis of O,S-dialkyl dithiocarbonates from alcohols using Mitsunobu’s reagent

A novel Mitsunobu-based protocol has been developed for the synthesis of O,S-dialkyl dithiocarbonates from a variety of primary, secondary and tertiary alcohols using carbon disulfide, in good to excellent yields. This protocol is mild and efficient compared to other reported methods.     

Nano TiO2/SO4 as a heterogeneous solid acid catalyst for the synthesis of 5-substited-1H-tetrazoles

An efficient and economical protocol for the synthesis of 5-substituted-1H-tetrazoles from various nitriles and sodium azide is reported using nano TiO₂/SO₄²⁻ as an effective heterogeneous catalyst. A wide variety of aryl nitriles underwent [3 + 2] cycloaddition to afford tetrazoles in good to excellent yields.     

CuFe2O4 nanoparticles: a magnetically recoverable and reusable catalyst for the synthesis of 5-substituted 1H-tetrazoles

An efficient and economical protocol for the synthesis of 5-substituted 1H-tetrazoles from various nitriles and sodium azide is described using magnetically recoverable and reusable CuFe₂O₄ nanoparticles. A wide variety of aryl nitriles underwent [2+3] cycloaddition under mild reaction conditions to afford tetrazoles in good to excellent yields. The catalyst was magnetically separated and reused five times without significant loss of catalytic activity.     

S-Benzyl isothiouronium chloride as a recoverable organocatalyst for the direct reductive amination of aldehydes

The direct reductive amination of aldehydes using S-benzyl isothiouronium chloride as a recoverable organocatalyst for the activation of the imine intermediate through hydrogen bonding is described. A mild and operationally simple fragment coupling procedure was accomplished with a wide range of aldehydes as well as amines in good to excellent yields. In addition, the S-benzyl isothiouronium chloride catalyst was easily recovered by simple filtration and reused without any drop in its efficiency.     

NH4I/EtOCS2K promoted synthesis of substituted benzils from diphenylacetylene derivatives

A facile protocol is described for the synthesis of benzil derivatives from readily accessible diarylacetylene derivatives using the NH₄I/EtOCS₂K system. This novel protocol results in excellent chemoselectivity and provided good to excellent yields. A control experiment indicated that the reaction proceeds via NH₄I promoted EtOCS₂K dimerization to give the corresponding dixanthogen and subsequent dixanthogen assisted oxidation.     

Metal-free selective synthesis of 2-substituted benzimidazoles catalyzed by Brönsted acidic ionic liquid: Convenient access to one-pot synthesis of N-alkylated 1,2-disubstituted benzimidazoles

A novel efficient method for the selective synthesis of 2-substituted benzimidazoles is described through condensation reaction of o-phenylenediamines with a wide rang of aliphatic, aromatic and heteroaromatic aldehyde substrates using Brönsted acidic ionic liquid as a reusable catalyst under metal-free conditions at ambient temperature. Notably, Dodecylimidazolium hydrogen sulfate ([DodecIm][HSO₄]) is the most efficient catalyst for good to excellent yields of the corresponding products (up to 98%). Subsequently, this protocol was successfully applied for the preparation of N-alkylated 1,2-disubstituted benzimidazoles in high to excellent yields via sequential one-pot reaction. In addition, catalysts are recycled at least four times without significant loss in activity.     

One-pot synthesis of aza-Morita-Baylis-Hillman adducts from α-oxo ketene-S,S-acetals, arylaldehydes and nitriles

Promoted by TiCl₄, a series of α-(1,3-dithiolan-2-ylidene)-β-amino carbonyl derivatives--the aza-Morita-Baylis-Hillman adducts, have been synthesized from α-oxo cyclic ketene-S,S-acetals, arylaldehydes, and nitriles in good to excellent yields. A mechanism involving sequential Morita-Baylis-Hillman and Ritter reactions for this novel one-pot, three-component reaction is described.     

Reductive carbonylation of aryl and heteroaryl iodides using Pd(acac)2/dppm as an efficient catalyst

Palladium catalyzed simple and efficient protocol for reductive carbonylation of aryl and heteroaryl compounds has been developed. The formylation of aryl and heteroaryl iodides takes place in the presence of Pd(acac)₂/dppm catalyst at 10 bar pressure of synthetic gas to give the desired aromatic and heteroaromatic aldehydes in good to excellent yields. Easy work-up, stability of the catalyst, low catalyst loading and less reaction time are the advantages of this method.     

An environmentally friendly,chemoselective, and efficient protocol for the preparation of coumarin derivatives by Pechman condensation reaction using new and reusable heterogeneous Lewis acid catalyst polystyrene-supported GaCl3

An environmentally benign Pechman protocol for the one-pot synthesis of 4-substituted coumarins through the condensation reactions of phenol substrates with β-ketoesters using polystyrene-supported GaCl₃ (PS–GaCl₃) as a highly active and reusable solid Lewis acid catalyst under mild and heterogeneous conditions in good to excellent yields is described. This new protocol is easy, simple, cost-effective, chemoselective, and in addition has the advantages of easy availability, stability, reusability and eco-friendly character of the catalyst, high to excellent yields, simple experimental and work-up procedure.     

Ferric sulfate [Fe2(SO4)3·xH2O]: an efficient heterogeneous catalyst for the synthesis of tetrahydroquinoline derivatives using Povarov reaction

Fe₂(SO₄)₃·xH₂O can be used as an efficient and reusable catalyst for the synthesis of pyrano- and furanotetrahydroquinolines via one-pot three-component Povarov reaction involving aromatic aldehydes, aromatic amines, and cyclic enol ethers. The catalyst is recyclable, economically viable, and environmentally benign. This protocol provides good yields and diastereoselectivity as well as applicability on a wide range of substrates.     

Copper fluorapatite catalyzed N-arylation of heterocycles with bromo and iodoarenes

Copper exchanged fluorapatite (CuFAP) is an effective heterogeneous catalyst for N-arylation of heterocycles with bromo- or iodoarenes using K₂CO₃ as base. N-Arylated products were isolated in good to excellent yields, demonstrating the versatility of the reaction.     

Copper-doped silica cuprous sulfate (CDSCS) as a highly efficient heterogeneous nano catalyst for synthesis of 3,5-disubstituted isoxazoles

A facile and highly efficient protocol for 1,3-dipolar cycloaddition of in situ generated nitrile oxides with terminal alkynes catalyzed by copper-doped silica cuprous sulfate (CDSCS) as a new and convenient heterogeneous nano catalyst is described. In this protocol, ‘click’ cycloaddition of various structurally diverse alkynes and imidoyl chlorides in the presence of CDSCS and NaHCO₃ in a solution of i-PrOH/H₂O (1:1, V/V) furnishes the corresponding 3,5-disubstituted isoxazoles in good to excellent yields at room temperature. CDSCS was approved as a chemically and thermally stable nano catalyst that can be recovered and reused for many consecutive trials without considerable decline in its reactivity.     

Candida antarctica lipase B-catalyzed synthesis of acetamides using [BMIm(PF6)] as a reaction medium

An efficient protocol has been developed for synthesis of acetamides using Candida antarctica lipase B (CaL B) in [BMIm(PF₆)] as a greener reaction medium. The reaction is applicable to a wide variety of aliphatic esters/acetic acid and amines providing excellent yields of corresponding acetamide. The catalyst exhibits remarkable activity and is reusable for up to four consecutive cycles.     

One-pot three-component reaction for the synthesis of biologically important spiro[benzo[f]quinoline-3,3′-indoline] derivatives

A previously unknown class of highly substituted benzoquinoline–spirooxindole are easily prepared by a novel application of a mild and efficient catalyst SbCl₃ for carbon–carbon and carbon–nitrogen bond formation reaction involving isatin, alkyne (dialkyl but-2-ynedioate) with aromatic amine (2-naphthylamine) in a one-pot three-component reaction. This protocol of one-pot synthesis afforded a library of dialkyl 2′-oxo-4H-spiro[benzo[f]quinoline-3,3′-indoline]-1,2-dicarboxylate derivatives, a potential bioactive compound in very good to excellent yields.     

BF3·SiO2: an efficient alternative for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes

Silica-supported boron trifluoride (BF₃·SiO₂) is an efficient, readily available, and reusable catalyst for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes by condensation of 2-naphthol and aldehydes. This reaction under heating or sonication conditions is very simple, affording good to excellent yields of products.     

The use of anhydrous CeCl3 as a catalyst for the synthesis of 3-sulfenyl indoles

Anhydrous CeCl₃ was successfully used as a catalyst for the synthesis of several 3-sulfenyl indoles in good to excellent yields through the reaction of indole with N-(alkylthio) and N-(arylthio)phthalimides in DMF.     

PtCl4-catalyzed cyclization of N-acetyl-2-alkynylanilines: A mild and efficient synthesis of N-acetyl-2-substituted indoles

An efficient synthesis of N-acetyl-2-substituted indole derivatives via direct intramolecular hydroamination of N-acetyl-2-alkynylaniline derivatives was developed. The reaction could be applied to a wide range of substrates employing only 1–2?mol% of PtCl₄ as the catalyst to furnish the desired indole products in moderate to excellent yields. The current protocol is efficient, reliable and scalable, and could serve as an important tool for convenient and rapid access to this important class of N-heterocyclic skeleton from readily available substrates.     

Development of a new class of (1S,3R,4R)-2-azabicyclo[2.2.1]heptane-oxazoline ligands and their application in asymmetric transfer hydrogenation

New 2-aza-norbornane-oxazoline compounds were synthesized and evaluated as ligands in the transfer hydrogenation of acetophenone. The best catalyst prepared in situ from [IrCl₂(COD)]₂ and a ligand afforded 1-(S)-phenylethanol in good yields and 79% ee.     

AcOH-catalyzed aza-Michael addition/N-nitrosation: An efficient approach to CF2HCH2-containing N-nitrosoamines

A simple and highly efficient protocol for the AcOH-catalyzed three-component reaction among nitroalkenes, difluoroethylamine and tert-butyl nitrite through cascade aza-Michael addition/N-nitrosation has been developed. A range of CF₂HCH₂-containing N-nitrosoamines were obtained in good to excellent yields. This approach features easily available cheap materials, without using additional organic solvents, simple operation under room temperature, gram scalable preparation and functionally diverse products.     

Palladium-catalyzed aziridination of alkenes using N,N-dichloro-p-toluenesulfonamide as nitrogen source

N,N-Dichloro-p-toluenesulfonamide (TsNCl₂) was found to be an efficient nitrogen source for the aziridination of unfunctionalized alkenes using palladium catalysts. Among the palladium salts, palladium acetate was the most effective catalyst for this reaction. A variety of alkenes were reacted at room temperature with TsNCl₂ to form the desired aziridines in moderate to good yields. This method can complement our previous protocol which is limited to the use of electron-deficient α,β-unsaturated alkenes.