Showing papers in "Tetrahedron Letters in 2011"

TL;DR: In this article, the one-pot three-component reaction for the synthesis of pyran annulated heterocycles is reported by condensing aromatic aldehydes, ethyl cyanoacetate, or malononitrile and C-H activated acidic compounds in the presence of catalytic amount of 4-(dimethylamino)pyridine (DMAP) in ethanol under reflux conditions.

TL;DR: In this paper, a one-pot practical, efficient, and environmentally benign multicomponent synthesis of 4H-pyrans and polysubstituted aniline derivatives of biological, pharmacological, and optical applications has been developed using a very mild, neutral, and reusable silica nanoparticles as catalyst.

TL;DR: In this paper, an assay to quantify the presence of aluminum ions with a receptor containing naphthol and quinoline moieties was developed using a turn-on fluorescence enhancement approach.

TL;DR: In this article, an efficient four-component synthesis of 6-amino-4-alkyl/aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles involving ethyl acetoacetate, hydrazine hydrate, malononitrile, and various aldehydes using l -proline (10 ǫ%) in water under mild reaction condition in excellent yields is established.

TL;DR: A library of benzimidazoles, benzoxazoles and benzothiazoles was efficiently synthesized by condensation of o-phenylenediamine, o-aminophenol, and oaminothiophenol respectively with aromatic aldehydes in the presence of catalytic amounts of Animal Bone Meal (ABM) and Lewis acids doped ABMs as mentioned in this paper.

TL;DR: An efficient and economical protocol for the synthesis of 5-substituted 1 H -tetrazoles from various nitriles and sodium azide is described using magnetically recoverable and reusable CuFe 2 O 4 nanoparticles as mentioned in this paper.

TL;DR: In this paper, γ-alumina is used as an expedient and recyclable catalyst for the synthesis of 6-amino-4-alkyl/aryl-3-methyl-2,4-dihydropyrano[2,3- c ]pyrazole-5-carbonitriles in water via a four-component reaction.

TL;DR: The Friedel-Crafts addition of indoles to α, β-unsaturated ketones, and nitro styrenes was studied with graphite oxide as catalyst.

TL;DR: In this paper, the synergistic effects of iron and copper in copper ferrite nanoparticles for the N-arylation of heterocycles with aryl halides were demonstrated.

TL;DR: In this paper, an iron oxide immobilized palladium catalyst was used for the N-alkylation of amines with alcohols under base and organic ligand free conditions.

TL;DR: A highly efficient diastereoselective one-pot synthesis of functionalized piperidines has been developed based on an aqua-compatible ZrOCl 2 ·8H 2 O catalyst via tandem reactions of aromatic aldehydes, amines, and acetoacetic esters.

TL;DR: In this article, the synthesis of dihydropyrimidinones via a clean multi-component Biginelli reaction under microwave irradiation is reported, which proved to be simple, efficient, economical, and environmentally friendly.

TL;DR: In this paper, the synthesis of benzimidazoles through the coupling of 1,2-phenylenediamine with aldehydes by using Co(OH)2 and similarly CoO(II) as efficient solid catalysts in ethanol at room temperature.

TL;DR: An efficient and green protocol for the synthesis of dihydropyrano[2,3-c]chromene derivatives by one-pot, three component coupling reaction of aromatic aldehyde, malononitrile, and 3-hydroxycoumarin has been developed using nano-structured ZnO as the catalyst.

TL;DR: A comparison of catalysts provides insight for the substrate scope and factors responsible for efficient catalytic activity and selectivity in the spirocyclization.

TL;DR: In this article, a task-specific ionic liquid, [Bmim]OH, has been used for an efficient synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones by one-pot cyclocondensation reaction of phthalhydrazide, aromatic aldehydes, and malononitrile or ethyl cyanoacetate under microwave irradiation.

TL;DR: In this article, the enantioselective tandem Michael addition-cyclization reaction between 3-methyl-2-pyrazolin-5-one and benzylidenemalononitriles was studied with modularly designed organocatalysts.

TL;DR: An efficient method for the Beckmann rearrangement of ketoximes to amides mediated by a catalytic amount of propylphosphonic anhydride (T3P®) is described in this article.

TL;DR: In this article, a cross-coupling protocol of thiourea, via cascade reaction with various substituted aryl halides, producing desired aryls, has an added advantage of avoiding foul-smelling thiols.

TL;DR: In this paper, pyrazolopyridine-spiroindolinones were prepared by the three-component reaction of 5-aminopyrazoles, isatin, and cyclic β-diketones in aqueous media and catalyzed by p -TSA.

TL;DR: Turn-on fluorescein-based chemosensors are highly sensitive and selective for Co2+ and Ni2+ in both absorption and emission modes, normally difficult to achieve with these paramagnetic ions as mentioned in this paper.

TL;DR: This marks the first time these two classes of cyclic imines have been found in the same organism, providing further evidence for a direct genetic relationship between the biosynthetic pathways for gymnodimines and spirolides suggested by comparison of their structures.

TL;DR: In this paper, a straightforward, efficient and more sustainable catalyst-free method was developed for the synthesis of quinoxaline, benzoxazole, and benzimidazole ring system in glycerol to achieve yields that were comparable to or better than, those in conventional media.

TL;DR: In this paper, a new strategy for building tubular structures from pillar-arenes 1 and 2 is presented. But the results described in this paper represent a new approach for building a tubular structure.

TL;DR: An organocatalytic asymmetric tandem 1,5-hydride transfer/ring closing reaction of o -aminobenzoketones with anilines to give cyclic aminals in fairly good diastereo- and enantioselectivities is described in this paper.

TL;DR: The elucidation of the reaction scope revealed that 5-aminopyrazoles, 3-amino-1,2,4-triazoles and 6-aminouracil could be used as the heterocyclic amine component.

TL;DR: Receptor 1 on binding with Zn2+ ion exhibits fluorescence enhancement which is due to the inhibition of the (ESIPT) mechanism.

TL;DR: In this paper, a simple, green and efficient protocol is developed in which zinc chloride-exchanged K10-montmorillonite (clayzic) is employed as a Lewis acid catalyst in aqueous media at room temperature for the synthesis of various benzimidazoles and quinoxalines from carbonyl compounds and o-phenylenediamine.

TL;DR: In this paper, a new, efficient, and environmentally benign protocol for the one-pot, four-component synthesis of 2,2-dimethyl-13-phenyl-2,3-dihydro-1 H -indazolo[2,1- b ]phthalazine-1,6,11(13 H )-trione by condensation of phthalic anhydride, hydrazinium hydroxide, aromatic aldehydes, and dimedone catalyzed by Ce(SO 4 ) 2 ·4H 2 O

TL;DR: In this article, a family of 2-amino-3-cyanopyridine derivatives are synthesized from aldehydes, ketones, malononitrile, and ammonium acetate via one-pot reaction catalyzed by ytterbium perfluorooctanoate [Yb(PFO)3].