Water mediated efficient one-pot synthesis of bis-(4-hydroxycoumarin)methanes

Abstract

Manganous chloride (MnCl₂·4H₂O) has been used as an efficient catalyst for an improved and rapid one-pot synthesis of bis-(4-hydroxycoumarin)methanes in excellent yields using water as a reaction medium. This aqueous mediated reaction of various aromatic and heteroaromatic aldehydes with 4-hydroxycoumarin using catalytic amounts of manganous chloride avoids the use of expensive, corrosive reagents, toxic solvents, and provides operational simplicity.     

An efficient green protocol for the synthesis of 2-aryl substituted benzothiazoles

Abstract

Cyclocondensation of 2-aminothiophenol and various aryl/heteryl aldehydes was carried in polyethylene glycol-400 as a catalyst and reaction medium at room temperature to obtain 2-aryl substituted benzothiazoles with excellent yields.     

IBX promoted one-pot condensation of β-naphthol,aldehydes, and 1,3-dicarbonyl compounds

Abstract

An efficient and mild protocol has been developed for one-pot condensation of β-naphthol, aldehydes, and 1,3-dicarbolyl compounds in presence of o-iodoxybenzoic acid has been found to be an excellent catalyst for the synthesis of tetrahydrobenzo[a]xanthen-one, 1H-benzo[f]chromen-2-yl)-one via one-pot three-component condensation of β-naphthol, aldehydes, and 1,3-dicarbonyl compounds. Short reaction time, ambient conditions, simple workup, and high yield with selective manner are some of the striking features of the present protocol.     

Efficient and green synthesis of 4H-pyrans and 4H-pyrano[2,3-c] pyrazoles catalyzed by task-specific ionic liquid [bmim]OH under solvent-free conditions

Abstract

A facile and convenient procedure for the synthesis of 4H-pyrans from aldehydes, malononitrile, and ethyl acetoacetate/acetylacetone and also synthesis of 4H-pyrano[2,3-c]pyrazoles from three-component condensation of aldehydes, malononitrile, and pyrazolone or four-component condensation of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine monohydrate using [bmim]OH as task-specific ionic liquid has been described. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium.

     

Synthesis of β-amino alcohols by ring opening of epoxides with amines catalyzed by cyanuric chloride under mild and solvent-free conditions

Abstract

The 2,4,6-trichloro-1,3,5-triazine catalyzed synthesis of β-amino alcohols by aminolysis of epoxide under solvent-free condition is described. Mild reaction conditions, short reaction times, inexpensive and readily available catalysts, and excellent yields of the products with high regioselectivity are attractive features of this methodology.     

Solvent-free chemoselective protection of aldehydes on the surface of alumina-sulfuric acid

Abstract

Chemoselective protection of alkyl and aryl aldehydes has been accomplished through the formation of dioxolane on the surface of alumina-sulfuric acid under solvent-free conditions where dialkyl ketones, aryl alkyl ketones, and diaryl ketones remain intact.     

An eco-friendly procedure for the efficient synthesis of arylidinemalononitriles and 4,4′-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols) in aqueous media

Abstract

Commercially available lithium hydroxide monohydrate (LiOH·H₂O) was found to be a novel “dual activation” catalyst for Knoevenagel condensation between malononitrile (1) or 3-methyl 1-phenyl-1H-pyrazol-5-(4H)-one (6) with aromatic aldehydes 2a–e leading to an efficient and easy synthesis of arylidenemalononitriles 3a–d and 4,4′-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols) 7a–c in short times. The reaction of aryl aldehydes with malononitrile afforded excellent yields after 1–6 min in aqueous media at room temperature. In case of 3-methyl-1-phenyl-1H-pyrazol-5-(4H)-one (6) and aromatic aldehydes afforded good yields after 60–75 min at 90°C.     

Green catalytic synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes using recyclable mesoporous zirconia modified with tungstophosphoric acid

Abstract

A simple and efficient procedure has been developed for the preparation of aryl-14H-dibenzo[a,j]xanthenes by a one-pot condensation of 2-naphthol and aryl aldehydes, in the presence of mesoporous zirconia modified with tungstophosphoric acid (ZrTPA60B_T100), to be used as a heterogeneous catalyst in a solvent-free medium using conventional heating. The present approach offers the advantages of clean reaction, simple methodology, short reaction time, and high yield. The reaction work-up is very simple and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions without appreciable loss of the catalytic activity.     

An efficient green protocol for the synthesis of chalcones by a Claisen–Schmidt reaction using bismuth(III)chloride as a catalyst under solvent-free condition

Abstract

An environmentally benign protocol for the synthesis of chalcones by the Claisen–Schmidt condensation of aldehydes with ketones using eco-friendly non-toxic bismuth(III)chloride catalyst under solvent-free condition is reported. In this protocol, the reaction time is very short, yields are high, and there are no other pollutants formed.     

A simple and highly efficient solvent- and catalyst-free synthesis of novel N-sulfamoyl imines

The reaction of aldehydes with primary sulfonamides under solvent- and catalyst-free conditions is described. This method affords the N-sulfamoyl imines in short reaction times and high yields. Mild conditions, simplicity, inexpensive and easily available reagents, and absence of any auxiliary substances are some other advantages of this procedure.     

Lithium bromide as an efficient,green, and inexpensive catalyst for the synthesis of quinoxaline derivatives at room temperature

Abstract

An efficient, simple, and green procedure for the synthesis of quinoxaline derivatives is described. The condensation of 1,2-diamines with 1,2-diketones using lithium bromide (LiBr) in H₂O/EtOH as a green reaction media at room temperature affords the title compounds in high to excellent yields and in short reaction times.     

An expeditious,highly efficient,catalyst and solvent-free synthesis of 9,10-dihydro-anthracene-9,10-α,β-succiniimide derivatives

Abstract

A simple, fast, and highly efficient protocol has been developed for the synthesis of 9,10-dihydro-anthracene-9,10-α,β-succinic imide derivatives by simple mixing and grinding of 9,10-dihydro-anthracene-9,10-α,β-succinic anhydride with various aliphatic, aromatic amines, and hydrazines. This catalyst and solvent-free green approach provided the condensation products within few minutes at room temperature in quantitative yield.     

Zirconium-catalyzed asymmetric Kabachnik–Fields reactions of aromatic and aliphatic aldehydes

An effective catalyst has been developed for the three-component reaction of aldehydes, anilines and phosphites in an asymmetric catalytic Kabachnik–Fields reaction to give α-aminophosphonates. A catalyst was sought that would give high asymmetric inductions for aromatic and, and more particularly, for aliphatic aldehydes since there has not previously been an effective catalyst developed for this class of aldehydes. The optimal catalyst is prepared from three equivalents of the 7,7′-di-t-butylVANOL ligand, one equivalent of N-methylimidazole and one equivalent of zirconium tetraisopropoxide. This catalyst was most efficient in the presence of 10 mol% benzoic acid. Optimal conditions for aryl aldehydes required the use of 3,5-diisopropyl-2-hydroxyaniline and gave the aryl α-aminophosphonates in up to 96% yield and 98% ee over 11 different aryl aldehydes. The best aniline for aliphatic aldehydes was found to be 3-t-butyl-2-hydroxyaniline and gave the corresponding phosphonates in up to 83% yield and 97% ee over 18 examples. The asymmetric inductions for aliphatic aldehydes were comparable with those for aromatic aldehydes with a mean induction of 90% ee for the former and 91% ee for the latter. The best method for the liberation of the free amine from the aniline substituted α-aminophosphonates involved oxidation with N-iodosuccinimide.

An effective catalyst has been developed for the three-component reaction of aldehydes, anilines and phosphites in an asymmetric catalytic Kabachnik–Fields reaction to give α-aminophosphonates.     

A highly efficient,operationally simple and selective thia-Michael addition under solvent-free condition

Abstract

The rapid and very simple conjugate addition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions in the presence of catalytic amount of lithium hydroxide at room temperature is reported. The reaction of aryl, alkyl, aliphatic, and hindered thiols with chalcone, enone, and nitrostyrene gave the corresponding Michael adducts with significant advantages, such as high conversions, short reaction time, mild reaction conditions, low cost, simple catalyst, and high to quantitative yields with excellent chemoselectivity.

     

Polyethylene glycol mediated facile protocol for N-Cbz protection of amines

Abstract

We have reported an efficient and eco-friendly protocol for the protection of various structurally and electronically divergent aryl and aliphatic amines using Cbz-Cl in the presence of polyethylene glycol (PEG)-400 at room temperature. The reaction afforded excellent yields with low as well as high molecular weight PEGs.     

Reaction of bromine with 4,5-dimethyl-1,4-cyclohexadiene-1,2-dicarboxylic acid: a green chemistry puzzle for organic chemistry students

Abstract

Bromination of an alkene is a typical addition reaction covered in an introductory organic chemistry course and laboratory. In this undergraduate organic chemistry laboratory exercise, students studied the bromination of a 4,5-dimethyl-1,4-cyclohexadiene-1,2-dicarboxylic acid. The reaction has an unexpected outcome as bromination yields the aromatic product, 4,5-dimethylphthalic acid. Green chemistry modification involves application of a “bromide/peroxide reaction” with NaBr/H₂O₂ in an acidic medium as an in situ source of bromine. The experiment was carried out as a two-day exercise and the students integrated molecular modeling, interpretation of mass spectra, knowledge of stability of organic compounds, and knowledge of the reaction mechanisms of addition and elimination to explain the experimental outcome.     

Morpholinium bisulfate [morH][HSO4]-promoted O,S, and Nacylation at room temperature

Abstract

Morpholinium bisulfate [morH][HSO₄] found to be highly inexpensive, efficient, and reusable catalyst to promote the acylation of phenols, thiols, alcohols, and amines in presence of acetic anhydride under solvent-free condition with excellent yields by stirring at room temperature. Present methodology deals with remarkable features of mild reaction condition, high yielding, shorter reaction time, easy workup, and more importantly, environmentally benign.     

Multicomponent eco-friendly synthesis of 3,4-dihydropyrimidine-2-(1H)-ones using an organocatalyst Lactic acid

Abstract

Biginelli compounds 3,4-dihydropyrimidine-2-(1H)-ones are synthesized in high yields via eco-friendly simple reaction procedure using Lactic acid: organocatalyst. The new method reported herein is green and is free of formation of any hazardous by products. The process has significant advantages over other reported methods.     

A very high yielding and facile alkaline earth metals homogeneous catalysis of Biginelli reaction: an improved protocol

Abstract

A high yielding and facile Biginelli reaction for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones and thiones, using inexpensive and available alkaline earth metal chlorides (MgCl₂, CaCl₂, SrCl₂ and BaCl₂) and acetic acid as the solvent in a homogeneous catalytic reaction, is reported.