Novel one-pot synthesis of 4H-chromene derivatives using amino functionalized silica gel catalyst

A simple, efficient, and environmentally benign method for the synthesis of 4H-chromene derivatives was developed using well ordered and recoverable amino functionalized silica gel as a base catalyst. The 4H-chromene derivatives were obtained in short time and excellent yield(87%–96%) by three component reaction of aldehydes, malononitrile and cyclic 1,3-diketones in water at 70 8C.     

Bi（OTf）3-catalyzed tandem reaction of naphthols with β,γ-unsaturated α-ketoesters. Efficient synthesis of functionalized 4H-chromenes

An efficient synthesis of functionalized 4H-chromenes by the tandem reaction of β,γ-unsaturated α- ketoesters with 2-naphthols, 1 -naphthols, and 1,3-dihydroxynaphthalenes has been accomplished with high selectivity and excellent yields in the presence of a catalytic amount of bismuth triflate [Bi（OTf）3, 5 mol%] under mild conditions. The functionalized 4H-chromene synthesis and our previous 2H- chromene hemiacetal synthesis could complement each other to enrich reaction diversity.     

Nucleophilic Vinylic Substitution in Perfluoroacylchromenes. Diastereoselective Synthesis of Push–Pull Enamino Ketones

Russian Journal of Organic Chemistry - The reactions of 2-perfluoroacyl-1H-benzo[f]chromenes and 6,7-dimethyl-3-trifluoroacetyl-4H-chromene with primary aliphatic amines and ammonia afforded a...     

A colorimetric and fluorescent turn-on sensor for pyrophosphate anion based on a dicyanomethylene-4H-chromene framework

A new red fluorescent sensor DCCP-Cu2+ based on dicyanomethylene-4H-chromene shows turn-on fluorescence with high selectivity for pyrophosphate over other anions.     

An efficient one-pot synthesis of indolyl-4H-chromene derivatives

Chemistry of Heterocyclic Compounds - A new one-pot three-component reaction for the synthesis of indolyl-4H-chromene derivatives has been developed. The synthesis was achieved by reacting...     

Evaluation of magnetically recyclable nano-Fe3O4 as a green catalyst for the synthesis of mono- and bis-tetrahydro-4H-chromene and mono and bis 1,4-dihydropyridine derivatives

Research on Chemical Intermediates - Magnetically separable Fe3O4 nanoparticles were used as an environmental friendly catalyst for the synthesis of mono- and bis-tetrahydro-4H-chromene and mono-...     

A new near-infrared fluorescent chemodosimeter for discrimination of sulfide from disulfide

Research on Chemical Intermediates - A new near-infrared fluorescent “turn-on” chemodosimeter (probe 1) based on dicyanomethylene-4H-chromene fluorophore for sulfide was developed....     

Synthèse du benzoyl-3 chromanol-4 et du benzoyl-3 2H-chromène

Reaction between phenylvinylketone and salicylaldehyde under basic conditions gave a mixture of 3-benzoyl-4-chromanol and 3-benzoyl-2H-chromene. Their structures were determined on the basis of analytical and spectroscopic data.     

Copper-catalyzed tandem reaction of 2-bromobenzyl bromides with 1,3-dicarbonyl compounds leading to 4H-chromenes

A Cu(Ⅰ)-catalyzed one-pot tandem reaction of 2-bromobenzyl bromides with 1,3-dicarbonyl compounds leading to 4H-chromene derivatives has been developed.This new approach toward 4H-chromenes combines several reactions in one pot and builds molecular complexity from readily available starting materials.     

Cascade reaction of β,γ-unsaturated α-ketoesters with phenols in trityl chloride/TFA system. Highly selective synthesis of 4-aryl-2H-chromenes and their applications

The treatment of β,γ-unsaturated α-ketoesters with phenols in the presence of trityl chloride and 4 ? molecular sieves in refluxing trifluoroacetic acid afforded 4-aryl-2H-chromenes in high yields, in which a reverse of the regiochemistry of J?rgensen-Rutjes chromane synthesis was observed. The isolation of 4H-chromene intermediates, confirmed by single-crystal X-ray analysis, indicates that the early stage of the reaction involves a Friedel-Crafts alkylation/cyclodehydration processes. Stirring of the 4H-chromene intermediate with trityl chloride in deuterotrifluoroacetic acid under reflux afforded the 2H-chromene and triphenylmethane in high yields, which implies the late stage of the reaction involves a hydrogen transfer process. Highly selective derivation of the hydroxyl esters to the corresponding hydroxyl amides, amino acids, amino esters and Friedel-Crafts adducts was further accomplished. Our endeavors will lead to a better understanding of the controlling elements behind their structural motifs. The products were confirmed unambiguously from their spectra and by single-crystal X-ray analysis.     

Ring-chain tautomerism and thermo- and photochromism of 3-(1-hydroxy-4-methyl-2-naphthyl)propenal imines

A series of previously undescribed 3-(1-hydroxy-4-methyl-2-naphthyl)propenal imines was synthesized. In the crystalline state all of the imines, except the N-(p-nitrophenyl)imine, have an open o-quinoid structure, whereas in solutions in nonpolar solvents they exist in the cyclic 2H-chromene form. In polar solvents the imines display ring-chain tautomeric equilibrium of the 2H-chromene and o-quinoid forms, the relative percentages of which are determined by the character of the substituent in the amino component of the molecule and by the polarity of the solvent. The N-(p-nitrophenyl)imine has-the 2H-chromene structure in the solid phase and in solvents.Communication 14 from the series Photochromic and thermochromic spirans. See [1] for communication 13.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1031–1039, August, 1983.     

Regioselectivity of reduction of 2-tert-butyl-1-benzopyrilium perchlorate

The reaction of 2-tert-butyl-1-benzopyrilium perchlorate with various reducing agents leads to a mixture of 2H- and 4H-chromenes. The greatest selectivity (90% 2-tert-butyl-4H-chromene and 10% 2H-isomer) was achieved using 1,3-dimethylbenzimidazoline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 313–315, March, 1989.     

Synthesis of Pterocarpan-Type Heterocycles via Oxidative Cycloadditions of Phenols and Electron-Rich Arenes

Oxidation of 4-alkoxyphenols or 4-methoxynaphthol with phenyl iodonium(bis)trifluoroacetate (PIFA) in the presence of electron rich 2H-chromenes or dihydronaphthalenes affords pterocarpans or 5-carbapterocarpans via a formal [3 + 2] cycloaddition process. Acid-catalyzed ionization of quinone dimethylmonoacetal in the presence of 7-methoxy-2H-chromene gave similar results, suggesting a phenoxonium ion intermediate in the oxidative process.     

Efficient and eco-friendly synthesis of 2-amino-4H-chromene derivatives using catalytic amount of tetrabutylammonium chloride (TBAC) in water and solvent-free conditions

A simple, efficient and eco-friendly procedure has been developed using tetrabutylammonium chloride as catalyst for the synthesis of 2-amino-4H-chromene derivatives in water and solvent-free neat conditions. The present methodology offers several advantages such as excellent yields, short reaction time and environmentally benign milder reaction conditions.     

Molecular structure of 2-(p-tolyl)ammo-5, 6-benzo-2H-chromene

An X-ray structural investigation (1274 reflections,R=0.057) has established that 2-(ptolyl)amino-5, 6-benzo-2H-chromene exists in the crystalline state as a cyclic 2H-chromene tautomer. This molecule is nonplanar due to the tetrahedral coordination of the C(1) atom and the relative rotation of phenyl and benzochromene rings.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 515–517, March, 1993.     

Synthesis of function-oriented 2-phenyl-2H-chromene derivatives using L-pipecolinic acid and substituted guanidine organocatalysts

Organocatalytic domino oxa-Michael/aldol reactions between salicylaldehyde with electron deficient olefins are presented. We screened guanidine, 1,1,3,3-tetramethylguanidine (TMG) and L-pipecolinic acid as organocatalysts for this transformation. 3-Substituted 2-phenyl-2H-chromene derivatives are synthesized with high yields and with poor enantioselectivity (5-17% ee) using L-pipecolinic acid while TMG works well with cinnamaldehyde without using co-catalyst. These 3-substituted-2-phenyl-2H-chromene derivatives are further derivatized to synthesize triazole and biotin-containing chromene derivatives, to facilitate purification of protein targets.     

Formation of benzofuran and 2H-chromene structures in one reaction. A novel synthesis of 2H-chromene derivatives

Heating the morpholinal of nitrosalicylic aldehyde with methyl propiolate in acetonitrile in the presence of Cul affords an equimolar mixture of 2-methoxycarbonylmethyl-3-morpholino-5-nitrobenzofuran and 3-methoxycarbonyl-2-morpholino-6-nitro-2H-chromene, the structures of which were determined by X-ray analysis. Only the 2H-chromene mentioned above was obtained in the absence of Cul and solvent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1222–1228, May, 1996.     

Synthesis and cytotoxic activity of 11-nitro and 11-amino derivatives of acronycine and 6-demethoxyacronycine

Condensation of 2-chloro-3-nitrobenzoic acid with either 5-amino-7-methoxy-2,2-dimethyl-2H-chromene or 5-amino-2,2-dimethyl-2H-chromene afforded diphenylamines 14 and 15. Trifluoroacetic anhydride mediated cyclization gave the corresponding acridones 16 and 17, which were subsequently N-methylated and reduced to 11-aminoacronycine and 11-amino-6-demethoxyacronycine. These two amino compounds, which gave stable water soluble salts, were 2- to 3-fold more potent than acronycine or 6-demethoxyacronycine in inhibiting L1210 cell proliferation.     

Enantioselective one-pot synthesis of 2-amino-4-(indol-3-yl)-4H-chromenes

An enantioselective one-pot synthesis of 2-amino-4-(indol-3-yl)-4H-chromenes via a Knoevenagel/Pinner/Friedel-Crafts reaction of salicylaldehyde, malononitrile, and indole is presented. Moderate to good yields (up to 89%) and high enantioselectivities (up to 90% ee) were obtained with an N,N'-dioxide-Zn(II) complex as the catalyst. This strategy provides an efficient and convenient method to access enantiomerically enriched 2-amino-4H-chromene derivatives.     

Design,Synthesis, and Antimicrobial Activity of (E)-4-Phenyl-2H-chromene-3-carbaldehyde O-[(1-Phenyl-1H-1,2,3-triazol-4-yl)methyl]oxime Derivatives

Russian Journal of Organic Chemistry - A new series of 1,4-disubstituted 1,2,3-triazole derivatives tethered to a 2H-chromene scaffold have been synthesized via a click reaction. The synthesized...