Indium trichloride catalyzed efficient one-pot synthesis of highly substituted furans

A one-pot synthesis of the substituted furans 3 could be achieved in good yields by reacting but-2-ene-1,4-diones 1 with acetoacetates 2 in the presence of a catalytic amount of InCl₃ (20 mol %) using i-PrOH as solvent at 80-90 °C for 4-8 h. InCl₃ was observed to give the optimum results among the various Lewis acids examined.     

1,4-Carbonylative addition of arylboronic acids to methyl vinyl ketone: a new synthetic tool for rapid furan and pyrrole synthesis

The rhodium catalysed 1,4-carbonylative addition of arylboronic acids to methyl vinyl ketone under carbon monoxide pressure was studied. High yields of 1,4-diketones were obtained using a catalytic system formed from Rh(COD)₂BF₄ (COD=1,5-cyclooctadiene) and triphenylphosphine even at very low catalyst loading (0.02 mol %). A short synthetic procedure combining this carbonylation reaction with a subsequent cyclisation step affords pyrroles or furans.     

Multinuclear NIR luminescent 1,4-BDC bridged Schiff-base complexes of Nd(III)

Solvent and reaction stoichiometry dictate the products isolated from reactions of the dinuclear precursor complex [ZnNdL(H₂O)(NO₃)₃] (H₂L = N,N′-bis(3-methoxy-salicylidene)ethylene-1,2-diamine) with the anionic multidentate linker 1,4-benzenedicarboxylate (1,4-BDC). With a 2:1 molar ratio of ZnNd:Na₂1,4-BDC in CH₃CN–EtOH the tetranuclear complex [Zn₂Nd₂L₂(1,4-BDC)(NO₃)₄(EtOH)₂] · 2MeCN (1) is produced while hexanuclear [Zn₄Nd₂L₄(1,4-BDC)₂] · (NO₃)₂ · 2Et₂O · 4H₂O (2) can be isolated from a DMF–EtOH mixture. A 4:1 mole ratio in DMF–EtOH gave the unusual polynuclear complex [Zn₄Nd₂L₄(1,4-BDC)₂] · [ZnNdL(NO₃)₃(OAc)]₂ (3). The NIR photophysical properties of the new compounds are reported.     

Gold-catalyzed cyclization of enyne-1,6-diols to substituted furans

Treatment of enyne-1,6-diols with 5 mol % Ph₃PAuCl in the presence of 5 mol % AgOTf as a cocatalyst selectively produced trisubstituted furans in good to excellent yields in dichloromethane at room temperature for 5-10 min through cyclization followed by isomerization.     

Synthesis of furans, pyrroles and pyridazines by a ruthenium-catalysed isomerisation of alkynediols and in situ cyclisation

Alkyne-1,4-diols are readily available substrates which are isomerised to 1,4-diketones using Ru(PPh₃)₃(CO)H₂/xantphos as a catalyst. In situ cyclisation into furans, pyrroles and pyridazines has been achieved under suitable conditions.     

Protonenkatalysierte gasphasendehydratisierung von 1,4-diketonen : Ein massenspektrometrisches analogon zur furansynthese in kondensierter phase

It is shown that the gas phase proton catalyzed dehydration of both 2,5-hexanedione (1a: R CH₃) and 1,4-diphenyl-1,4-butanedione (1b: R Ph) yields protonated 2,5-disubstituted furans. the addition of H₃O⁺ to furans followed by ring opening and formation of protonated diketones has not been achieved. Reaction of 1a,b with NH₄⁺/NH₃ does not result in the formation of pyrrole. The main reaction corresponds to the formation of cluster ions, i.e. proton bounded dimers and trimers of diketone and ammonia.     

A simple and convenient synthesis of substituted furans and pyrroles by CuCl2-catalyzed heterocyclodehydration of 3-yne-1,2-diols and N-Boc- or N-tosyl-1-amino-3-yn-2-ols

A simple and economical synthesis of substituted furans and pyrroles, by ligand-free CuCl₂-catalyzed heterocyclodehydration of readily available 3-yne-1,2-diols and N-Boc- or N-tosyl-1-amino-3-yn-2-ols, respectively, is presented. Reactions are carried out in MeOH at 80-100 °C for 1-24 h and afford the corresponding heterocyclic derivatives in 53-99% isolated yields.     

One-pot synthesis of 1,4-diarylsubstituted 1,3-diynes from the sequential coupling reactions of aryl iodides and propiolic acid

1,4-Disubstituted 1,3-dialkynes were obtained from the one-pot palladium/copper-catalyzed coupling reactions of aryl iodide and propiolic acid. The optimized catalytic system consisted of 5.0 mol % Pd(PPh₃)₂Cl₂, 10 mol % dppb, 10 mol % CuI, 2.4 equiv of DBU, and 1.2 equiv of K₂CO₃. The coupling reaction was carried out at 30 °C for 6 h and subsequently at 80 °C for 3 h.     

Coordination modes of 1,2,3,4-tetrahydro-1,4-diphenyl-1,4-benzodiphosphinine (bedip) to Pt and Pd metal ions: Synthesis and structural characterization of mono- and bi-nuclear complexes

Within this study, coordination properties of the cyclic diphosphine 1,2,3,4-tetrahydro-1,4-diphenyl-1,4-benzodiphosphinine (bedip) are investigated, through the preparation of neutral and cationic Pt(II), Pt(IV) and Pd(II) complexes. The diphosphine acts as bridging ligand in the neutral Pt(II) and Pd(II) complexes, affording [MX(CH₃)(μ-bedip)]₂ (X = Cl, Br, I, CH₃) species. Chelation is observed in all the remaining complexes. The molecular structures of [PtX(CH₃)(μ-bedip)]₂ (X = Br, I) and [PtI(CH₃)₃(bedip)] are also determined.     

Synthesis characterization and X-ray crystal structures of cis-1,4-diaminocyclohexane-platinum(II) nucleobase adducts

Platinum complexes of the type [Pt(cis-1,4-DACH)(L)₂]X, where cis-1,4-DACH = cis-1,4-diaminocyclohexane; L = adenine (ade) (1), hypoxanthine (hyp) (2), 9-methylguanine (9-megua) (3), cytosine (cyt) (4), or 1-methylcytosine (1-mecyt) (5); and X = SO₄ or Cl₂ groups, were synthesized and characterized by elemental analysis and by ¹H, ¹³C, and ¹⁹⁵Pt nuclear magnetic resonance spectroscopy. The crystals of [Pt(cis-1,4-DACH)(9-megua)₂]SO₄[9-megua-H]₂SO₄ (3) and [Pt(cis-1,4-DACH)(1-mecyt)₂]Cl₂ · 6H₂O (5) were also subjected to single-crystal X-ray diffraction. The base/PtN4 coordination plane dihedral angles were 74.55° and 85.61° in complex 3 and 78.12° and 81.80° in complex 5. The platinum had distorted square planar geometry in both complexes; the two adjacent corners were occupied by the two nitrogen atoms of cis-1,4-DACH, and the other two corners were occupied by the two N7 atoms of 9-megua in complex 3 and the two N3 atoms of 1-mecyt in complex 5. The cis-1,4-DACH, which has a unique twist-boat configuration, formed a seven-member chelating ring with platinum, which led to considerable strain during bidentate cis-1,4-DACH binding. Cations of both complexes 3 and 5 adopted C₂ molecular symmetry. These adducts were the models for the intrastand cross-links that were relevant to the binding of the Pt(II) antitumor drugs to DNA.     

Dinuclear copper complexes with cyanamide derivatives as bridging ligands

Three mixed-valence copper complexes [{Cu(phen)₂}₂(μ-L)](PF₆)₂ (where phen = 1,10-phenanthroline, L = 1,4-dicyanamidobenzene (dicyd)), 1,4-dicyanamido-2,5-dimethylbenzene (Me₂dicyd) and 1,4-dicyanamido-2,5-dichlorobenzene (Cl₂dicyd), and one dinuclear Cu(II) complex [{Cu(phen)₂}₂(μ-apc)](PF₆)₃ (where apc = monoanion of 4-azo(phenylcyanamido)benzene) have been prepared and characterized by elemental analysis, IR and electronic absorption spectroscopies and cyclic voltammetry. [{Cu(phen)₂}₂(μ-apc)](PF₆)₃ · 2CH₃COCH₃ crystallized in the triclinic system and both five-coordinate Cu(II) ions in the dinuclear unit are linked through a bridging 4-azo(phenylcyanamido)benzene (apc) ligand. The cyanamide group (NCN) of the bridging ligand is coordinated to Cu(II) ions through the cyano-nitrogen and amido-nitrogen. The bond length between Cu(1) and cyano-nitrogen is slightly larger than that formed by Cu(2) and amido-nitrogen. The angular structural index parameters, τ, for Cu(1) and Cu(2) are 0.9 and 0.5, respectively. The copper(II) atoms display a different geometry with a N₅ chromophore group. The intra Cu?Cu separation is 5.156(1) Å. All of the dicyd dinuclear copper complexes show radical anion absorption.     

Stereospecific preparation of symmetrical (1Z, 3Z)- and (1E, 3E)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes from 1-bromo-1-fluoroalkenes

A straightforward method to prepare symmetrical (1Z, 3Z)- and (1E, 3E)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes is described. High E/Z ratio 1-bromo-1-fluoroalkenes, prepared by isomerization from the E/Z ≈ 1:1 isomeric mixtures, reacted with Bu₃SnSnBu₃ and Pd(PPh₃)₄ to afford (1Z, 3Z)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes in good yield. (Z)-1-Bromo-1-fluoroalkenes, which were prepared by kinetic reduction from 1-bromo-1-fluoroalkenes (E/Z ≈ 1:1), can undergo similar reaction with Bu₃SnSnBu₃ and Pd(PPh₃)₄/CuI to prepare (1E, 3E)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes.     

Triphenylpyrylium salt-sensitized photoreactions of 1,4-diaryl-2,3-dioxabicyclo[2.2.2]octanes through competitive single electron-transfer pathway and proton-catalyzed pathway

2,4,6-Triphenylpyrylium tetrafluoroborate (TPPBF₄)-sensitized photoinduced electron-transfer (PET) reactions of 1,4-diaryl-2,3-dioxabicyclo[2.2.2]octanes 5 (a: Ar¹ = Ar² = p-MeOC₆H₄, b: Ar¹ = Ar² = p-MeC₆H₄, c: Ar¹ = Ar² = Ph) underwent novel fragmentation through their radical cations to give 1,4-diarylbutan-1,4-diones 6 accompanied by elimination of ethylene. On the other hand, 4-aryl-cyclohex-3-en-1-ones 7, p-substituted phenols 8, and 4-aryl-4-aryloxycyclohexanones 9 were produced through proton-catalyzed pathways when the PET reactions of 5 were performed in the absence of a certain base such as 2,6-di-tert-butylpyridine (DTBP). Particularly, the formation of 9 is consistent with the novel cationic rearrangement involving nucleophilic O-1,2-aryl shifts and C-1,4-aryl shifts.     

Effect of capping and particle size on Raman laser-induced degradation of γ-Fe2O3 nanoparticles

Diol capped γ-Fe₂O₃ nanoparticles are prepared from ferric nitrate by refluxing in 1,4-butanediol (9.5 nm) and 1,5-pentanediol (15 nm) and uncapped particles are prepared by refluxing in 1,2-propanediol followed by sintering the alkoxide formed. X-ray diffraction (XRD) shows that all the samples have the spinel phase. Raman spectroscopy shows that the samples prepared in 1,4-butanediol and 1,5-pentanediol and 1,2-propanediol (sintered at 573 and 673 K) are γ-Fe₂O₃ and the 773 K-sintered sample is Fe₃O₄. Raman laser studies carried out at various laser powers show that all the samples undergo laser-induced degradation to α-Fe₂O₃ at higher laser power. The capped samples are however, found more stable to degradation than the uncapped samples. The stability of γ-Fe₂O₃ sample with large particle size (15.4 nm) is more than the sample with small particle size (10.2 nm). Fe₃O₄ having a particle size of 48 nm is however less stable than the smaller γ-Fe₂O₃ nanoparticles.     

Characterization of two linear chain compounds: Ferromagnet NiCl2(CH3OH)2(1,4-dioxane)0.5 (1) and paramagnet [NiCl2(H2O)2(1,4-dioxane)](1,4-dioxane) (2)

The solvent-mediated crystal-to-crystal transformation was observed from yellow crystal of NiCl₂(CH₃OH)₂(1,4-dioxane)_0.5 (1) to green crystal of [NiCl₂(H₂O)₂(1,4-dioxane)](1,4-dioxane) (2) under high humidity or adding of H₂O in CH₃OH/1,4-dioxane solution. The μ-Cl₂ bridge in 1 replaced by 1,4-dioxane bridge in 2. In 1, the chlorine-bridged linear chains of NiCl₂(CH₃OH)₂ and 1,4-dioxane molecules stack along the b- and c-axis alternatively with hydrogen bonds intrachain, interchain, between chain and solvent. These hydrogen bonds and dipolar interaction between ferromagnetic coupling chlorine-bridged chains result in long-range ferromagnetic ordering at 3.1 K and a strong frequency dependence of the ac-susceptibilities associated to domain structures with very large shape anisotropy was observed below 3.1 K. In 2, layers of 1,4-dioxane-bridged linear chains of NiCl₂(H₂O)₂(1,4-dioxane) are intercalated by layer of 1,4-dioxane molecules with hydrogen bonds between chain and solvent. Compound 2 is paramagnet to 2 K.     

Three novel Cd(II) coordination polymers: Synthesis,crystal structures,fluorescence and thermal properties

Three novel Cd(II) coordination polymers, {[Cd(C₄BIm)(N₃)(OAc)]·C₂H₅OH}_n (1), [Cd(C₄BIm)(H₂O)₃(SO₄)]_n (2) (C₄BIm = 1,4-bis(benzimidazolyl)butane) and [Cd(bbbm)_1.5(NO₃)₂]_n (3) (bbbm = 1,1′-(1,4-butanediy)bis-1H-benzimidazole) have been prepared and characterized spectroscopically and crystallographically. In polymer 1, C₄BIm–Cd chains and N₃–Cd chains criss-cross to a layer structure. Polymer 2 possesses a concave–convex chain structure. Polymer 3 exhibits a two-dimensional (2-D) rhomboid grid network, the dimensions of the grid is 25.807 × 13.771 Å, and the diagonal-to-diagonal distances are 28.608 × 21.145 Å. The fluorescence properties and the thermal stabilities of the three polymers were investigated.     

Indium trichloride catalyzed three component one-pot route to 1-hydroxymethyl-3-aminomethyl indoles

A one-pot synthesis of 1-hydroxymethyl-3-aminomethyl indoles 3 could be achieved in excellent yield by reacting indoles 1 with formaldehyde and secondary amines 2 in the presence of molecular sieves (3 Å) and catalytic amount of InCl₃ (10 mol %) in 1,4-dioxane at room temperature for 3-5 h.     

Cross coupling of 3-bromopyridine and sulfonamides (RNHSO2R·R = H, Me, alkyl; R = alkyl and aryl) catalyzed by CuI/1,3-di(pyridin-2-yl)propane-1,3-dione

N-(3-Pyridinyl)-substituted secondary and tertiary sulfonamides have been synthesized in good to excellent yields by the reaction of 3-bromopyridine with primary and secondary alkyl and aryl sulfonamides (MeSO₂NH₂, MeSO₂NHMe, TolSO₂NH₂, TolSO₂NHMe, 1,3-propanesultam, and 1,4-butanesultam), catalyzed by CuI (20 mol %) and 1,3-di(pyridin-2-yl)propane-1,3-dione (20 mol %) with K₂CO₃ (200 mol %) in DMF (0.17 M for ArBr) at 110-120 °C over 36-40 h. 2-Bromopyridine, 4-bromopyridine, and a wide variety of substituted phenyl bromides can also be successfully coupled with sulfonamides under these reaction conditions.     

Thermophysical properties of sulfur heterocycles: Thiane and thiophene derivatives

The present study reports a DSC study of the sulfur heterocyclic compounds: 2,2’-bithiophene [492-97-7]; 2,5-thiophenedicarboxylic acid [4282-31-9]; 3-acetylthiophene [1468-83-3]; 2-thiopheneacetic acid [1918-77-0]; 3-thiopheneacetic acid [6964-21-2]; 1,4-dithiane sulfone [139408-38-1]; 1,3-oxathiane-3,3-dioxide (1,3-oxathiane sulfone) [109577-03-9] and 1,4-oxathiane-4,4-dioxide (1,4-oxathiane sulfone) [107-61-9] in the temperature interval T = 268 K and the melting temperatures. Temperatures, enthalpies and entropies of fusion are reported. 1,4-Oxathiane sulfone presents solid-solid phase transitions near to fusion. No additional solid-solid phase transitions were observed for the other solid compounds. For the compounds that are solids over the temperature interval, the heat capacity of the condensed phase was measured. Heat capacities at T = 298.15 K for the liquids 2-acetylthiophene [88-15-3]; methyl, 2-thiopheneacetate [19432-68-9]; methyl, 3-thiopheneacetate [58414-52-1] and thiazole [288-47-1] were also measured. The C_p,m (298.15 K) values obtained in this work were compared with the available experimental data and with values estimated with group contribution schemes.     

A one-pot synthesis of 2,3-dihydro-1H-pyrrolo[3,2-c]quinolines

A one-pot synthesis of the 2,3-dihydro-1H-pyrrolo[3,2-c]quinoline core from substituted 2-iodoanilines and 2,3-dihydro-1H-pyrrole was achieved using 10 mol % Pd(PPh₃)₄, and K₂CO₃ in 1,4-dioxane at 170 °C for 1 h in a microwave oven. This reaction can be carried out on a gram scale. The proposed mechanism involves a Heck-coupling reaction followed by intra-molecular Schiff base formation and double bond migration.