Efficient synthesis of 3,3′,5,5′-tetra(p-X-phenylethynyl)biphenyl (X: NMe2; OMe) by homocoupling of 1-bromo-3,5-di(p-X-phenylethynyl)benzene or by heterocoupling of 3,3′,5,5′-tetraethynylbiphenyl with p-X-phenylbromobenzene with nickel or palladium complexes, respectively

The conjugated 3,3′,5,5′-tetra(p-X-phenylethynyl)biphenyl derivatives were efficiently obtained by homocoupling of 1-bromo-3,5-di(p-X-phenylethynyl)benzene mediated by zero-valent nickel complexes.The 1-bromo-3,5-di(p-X-phenylethynyl)benzene was previously prepared by heterocoupling between 1-bromo-3,5-di(ethynyl)benzene and p-X-iodobenzene (X: NMe₂; OMe) catalysed by the palladium/copper system in good yield. The necessary 1-bromo-3,5-di(ethynyl)benzene was obtained by heterocoupling between 1,3,5-tribromobenzene and 2-methyl-3-butyn-2-ol catalysed by palladium and successive treatment with sodium hydroxide in dry toluene, in good yield.The same 3,3′,5,5′-tetra(p-X-phenylethynyl)biphenyl (X: NMe₂; OMe) derivatives were alternatively synthesised in highest yield by heterocoupling between 3,3′,5,5′-tetra(ethynyl)biphenyl and p-X-bromobenzene (X: NMe₂; OMe) catalysed by palladium in excellent yields. Previously, 3,3′,5,5′-tetra(ethynyl)biphenyl was obtained in practically quantitative yield by homocoupling of 1-bromo-3,5-di[4-(2-methyl-3-butyn-2-ol)] benzene mediated by the zero-valent nickel complex to the 3,3′,5,5′-tetra{di[4-(2-methyl-3-butyn-2-ol)]}biphenyl followed the treatment with sodium hydroxide.     

Synthesis of conjugated (1E,3E)- and (1Z,3Z)-1,4-di(n-pyridyl) (or n-quinolyl)-1,3-butadienes from n-(2′-chloroethenyl)pyridine (or quinoline)

The homocoupling reaction between the conjugated n-(2-chloroethenyl)pyridine; n, 2-, 3- and 4- (or quinoline; n, 2- and 4-) mediated by zero-valent nickel complexes at room temperature affords to the corresponding 1,4-diaryl-1,3-butadiene, always as the 1E,3E stereoisomer. The yield in 1,4-diaryl-1,3-butadiene increases with the nickel catalyst and hence, the active zero-valent nickel catalyst is not regenerated during the homocoupling reaction.The stereospecific synthesis of (1Z,3Z)-1,4-di(4′-pyridyl)-1,3-butadiene stereoisomer was efficiently carried out by partial hydrogenation of the appropriate 1,4-di(4′-pyridyl)-1,3-butadiyne.     

Synthesis and optical properties of conjugated N,N-dimethyl and thienyl end-capped 2,5-(arylethynyl)thiophene oligomer structures

End-capped (N,N-dimethylaminophenyl) and 2′-thienylethynyl 2,5-thiophene oligomer structures were synthesized by heterocoupling between the terminal acetylenes such as: p-(N,N-dimethylaminophenyl)ethyne (3) [or 1-(p-(N,N-dimethylaminophenyl)-2-p-(ethynylphenyl)ethyne, 4]; p-(β-ethenyl-2′-thienyl)phenylethyne (E-9) [or p-(β-ethynyl-2′-thienyl)phenylethyne, 11], and 2,5-diiodothiophene, catalyzed by the Cl₂Pd(PPh₃)₂/CuI system, in good to excellent yields. The 2,5-di[(3′,5′-di(trimethylsilylethynyl)phenyl]_x-1-ethynyl]thiophene oligomers were prepared by heterocoupling between 3′,5′-di[(trimethylsilylethynyl)phenyl]_x-1-ethyne (n = 0-2) terminal acetylenes and 2,5-diiodothiophene, in excellent yields. The terminal acetylenes were efficiently prepared by a specific protection-deprotection methodology. All the ethynylphenyl compounds obtained show fluorescence radiation emission, with a bathochromic shift of the wavelength that increases with the chain conjugation.     

Hydrodehalogenation of halogenated pyridines and quinolines by sodium borohydride/N,N,N′,N′-tetramethylethylenediamine under palladium catalysis

A protocol for the hydrodehalogenation of halogenated pyridines and quinolines by the sodium borohydride/N,N,N′,N′-tetramethylethylenediamine (NaBH₄-TMEDA) system under palladium catalysts is reported. Catalytic amounts of [1,1′-bis(diphenylphosphino)ferrocene] dichloropalladium(II) in combination with NaBH₄-TMEDA rapidly hydrodehalogenate chloro(bromo)-pyridines and -quinolines at room temperature in quantitative yields. Chemoselective reduction of 4,7-dichloroquinoline affords 7-chloroquinoline as the sole product in almost quantitative yield. Moreover, palladium(II) acetate-triphenylphosphine and NaBH₄-TMEDA are able to reduce efficiently reactive bromo-pyridines and -quinolines.     

Salen and half-salen palladium(II) complexes: synthesis, characteriztion and catalytic activity toward Suzuki-Miyaura reaction

Salen and half-salen palladium(II) complexes (salden)Pd (1, salden=N,N′-bis(3,5-di- tert-butylsalicylidene)-1,2-dimethylethylenediamine), (hsalph)PdCl (2, hsalph=3,5-di-tert- butylsalicylidene-1-iminophenylene-2-amine), and (salph)Pd (4, salph=N,N′-bis(3,5-di-tert- butylsalicylidene)-1,2-phenylenediamine) were prepared and structurally characterized by X-ray crystallography. Complex 2 proved to exhibit high catalytic activity toward Suzuki-Miyaura reaction. Polyaromatic C₃-symmetric derivatives and various fluorinated biphenyl derivatives were readily achieved in good yields using Suzuki-Miyaura reaction catalyzed by complex 2.     

Synthesis of conjugated 2 and 2,5-(ethenyl) and (ethynyl)phenylethynyl thiophenes: fluorescence properties

Nano conjugated thienylethenyl and thienylethynyl compounds with controlled structure and dimensions have been efficiently prepared, by heterocoupling reaction between 1,4-(thienylethynyl)phenylacetylene (or thienylethenyl)phenylacetylene and 2- or 2,5-dihalothiophene. Conjugated 1,4-di(2-thienylethynylphenyl)- (or 2-thienylethenylphenyl)-1,3-butadiyne were obtained by the homocoupling of the terminal acetylenes in excellent yield. The end-capped (N,N-dimethylaminophenyl)- and [3,5-di(trimethylsilylethynyl)-1-ethynyl]-2,5-di(phenylethynyl)_nthiophene were obtained by the heterocoupling between the corresponding terminal acetylene and 2,5-di(iodo)thiophene, catalyzed by the bis(triphenylphosphine)palladium and cuprous iodide system in excellent yield.     

Synthesis of conjugated 2,7-bis(trimethylsilylethynyl)-(phenylethynyl)nfluoren-9-one and 9-(p-methoxyphenyl)-9-methyl derivatives: optical properties

2,7-Substituted 9-fluorenones and 9,9-disubstituted fluorene have been synthesized and their fluorescence properties analyzed. The synthesis of conjugated 2,7-bis(trimethylsilylethynyl)-(phenylethynyl)_nfluoren-9-one (or the 9-(p-methoxyphenyl)-9-methyl) structures was carried out by the heterocoupling reaction between the 2,7-di(halo)fluoren-9-one (or 2,7-dibromo-9-(p-methoxyphenyl)-9-methylfluorene) and p-trimethylsilylethynyl(phenylethynyl)_n (n=1,2), catalyzed by the dichloro bis(triphenylphosphine)palladium and cuprous iodide system, in a divergent synthesis.The π-extended conjugated compounds exhibit fluorescence radiation emission (blue light-emitting), with important quantum yield for the 9-(p-methoxyphenyl)-9-methyl-2,7-bis(trimethylsilylethynyl)-(phenylethynyl)_nfluorenes which increases with the conjugation.     

I2-catalyzed base-free cyclization of 3-homoallylquinoline-2-thiones: facile synthesis of tetracyclic,furothiopyrano[2,3-b]quinolines

I₂-catalyzed base-free reactions of 3-homoallylquinoline-2-thiones have been described for the synthesis of tetracyclic quinolines, tetrahydrofuro [2′,4′:4,6]thiopyrano[2,3-b]quinolines in excellent yields. Similarly, I₂-catalyzed reactions could proceed to tricyclic quinolines from hydroxyl group protected 3-homoallylquinoline-2-thiones. However, deprotection of group in tricyclic quinoline with HI again transformed into tetracyclic quinoline. The sulfonium salt intermediate has been proposed to explain these reactions.     

Synthesis and polymerization of 5‐(N,N‐dimethylamino)naphthylacetylene with homogeneous rhodium and palladium complexes

The monomer 5‐ethynyl‐N,N‐dimethylnaphthalen‐1‐amine ( 2 ) was satisfactorily obtained by a heterocoupling reaction between 5‐iodo‐(N,N‐dimethyl)naphthalen‐1‐amine and 2‐methyl‐3‐butyn‐2‐ol catalyzed by a palladium–copper system and followed by acetone elimination. Poly(5‐ethynyl‐N,N‐dimethylnaphthalen‐1‐amine) was isolated by the reaction of 2 in the presence of homogeneous rhodium and palladium complexes. On the basis of the spectroscopic data, the polymer always showed a cis–transoidal, stereoregular structure. Moreover, only with the rhodium catalyst in methanol was a dimeric product isolated in a very low yield, having a conjugated terminal ene–yne structure, which permitted the consideration of a metallated chain‐transfer intermediate in the polymer propagation. The kinetics of the catalyzed reaction were analyzed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 437–446, 2007     

Phosphine-free Pd-salen complexes as efficient and inexpensive catalysts for Heck and Suzuki reactions under aerobic conditions

Phosphine-free palladium-salen complexes, N,N′-bis(salicylidene)-ethylenediamino-palladium and N,N′-bis(salicylidene)-1,2-phenylenediamino palladium, are found to be highly active catalysts for the Heck olefination of aryl iodides and Suzuki reaction of aryl iodides and bromides giving excellent yields (70-90%) of products under aerobic conditions, in short reaction times (10-60 min).     

Synthesis of 1H-pyrrolo[3,2-c]quinoline derivatives via palladium-catalyzed heteroannulation of 2-aryl-3-iodo-4-(phenylamino)quinolines and 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinolines

Palladium(0)/copper iodide catalyzed Sonogashira cross-coupling of 2-aryl-3-iodo-4-(phenylamino)quinolines with terminal alkynes afforded series of 1,2,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines in a single-step operation. Conversely, the 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were found to undergo PdCl₂(PPh₃)₂/CuI catalyzed intramolecular Heck reaction to yield the corresponding 1,3,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines.     

Asymmetric Friedel-Crafts alkylation of activated benzenes with methyl (E)-2-oxo-4-aryl-3-butenoates catalyzed by [Pybox/Sc(OTf)3]

The asymmetric Friedel-Crafts reaction between methyl (E)-2-oxo-4-aryl-3-butenoates (1a-c) and activated benzenes (2a-d) has been efficiently catalyzed by the Sc^III triflate complex of (4′S,5′S)-2,6-bis[4′-(triisopropylsilyl) oxymethyl-5′-phenyl-1′,3′-oxazolin-2′-yl]pyridine (pybox 3). The 4,4-diaryl-2-oxo-butyric acid methyl esters (4) are usually formed in good yields and the enantioselectivity is up to 99% ee. The sense of the stereoinduction can be rationalized with the same octahedral complex (10) between 1, pybox 3 and Sc triflate already proposed for other reactions involving pyruvates, and catalyzed by the same complex.     

Polymerization of conjugated 5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine with rhodium and palladium complexes

The monomer 5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine was satisfactory obtained through the heterocoupling reaction of 5‐ethynyl‐N,N‐dimethylnaphthalen‐1‐amine and 4‐(5‐iodo‐1‐naphthyl)‐2‐methyl‐3‐butyn‐2‐ol catalyzed by a palladium–copper system, followed by acetone elimination. Poly{5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine} was obtained through the reaction of the acetylene monomer with homogeneous rhodium and palladium catalyst complexes. The structure of the polymers always showed a trans–cisoidal chain configuration on the basis of IR and NMR spectra. Moreover, only for the rhodium catalyst complex in methanol was a dimeric product isolated in a very low yield, having a conjugated terminal ene–yne structure, which permitted the consideration of a metallated chain‐transfer intermediate in the polymer propagation. The mass determination of the polymers, by osmometry and gel permeation chromatography techniques, showed low average molecular weights. The kinetics of the catalyzed polymerization were analyzed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2038–2047, 2007     

A novel strategy for the synthesis of 6H-chromeno [4, 3-b] quinoline by intramolecular Heck cyclization

A novel procedure for the synthesis of various derivatives of 6H-chromeno [4, 3-b] quinolines from intramolecular Heck reaction of 2-chloro-3-(phenoxymethyl) quinolines is described in this study. Intramolecular cyclization of N-alkylated indoles was efficiently investigated as well. The reaction is catalyzed by bis (triphenylphosphine) palladium (II) dichloride in acetonitrile at 80 °C.     

Arene-promoted lithiation of 1,n-dihaloalkanes (n=2-6): a comparative study

The reaction of 1,n-dichloroalkanes 3a (n=2-6) with an excess of lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB; 2.5 mol %) in the presence of different carbonyl compounds [Bu^tCHO, PhCHO, Et₂CO, (CH₂)₄CO, (CH₂)₅CO, (CH₂)₇CO, (−)-menthone], in THF at −78 °C leads, after hydrolysis with water, to the expected 1,(n+2)-diols 4, yields being <25% for n=2, 3 and in the range of 45-79% for n=4-6. When the same protocol is applied to 1,n-bromochloroalkanes 3b and 1,n-dibromoalkanes 3c (n=2-6), diols 4 are obtained in general with lower yields.     

Synthesis of terpyridine-substituted calix[n]arenes

Calix[n]arenes (n = 4,5) comprising 4-(2,2′:6′,2″-terpyridyl)-phenyl substituents at the upper rim were synthesized for the first time, employing Suzuki-type coupling reactions. All calix[n]arene derivatives were prepared as cone conformers. The single crystal X-ray structure of cone-5,11,17,23-tetra{4-(2,2′:6′,2″-terpyridyl)-phenyl}-25,26,27,28-tetrabutoxycalix[4]arene 4 is analyzed in terms of structural rigidity and potential use of these ligands as novel synthons of cage-type metallosupramolecular assemblies.     

A highly emissive cruciform triarylborane as a ratiometric and solid state fluorescence sensor for fluoride ions

We disclosed a novel cruciform tri-coordinate organoboron compound, 2′,5′-bis{[(4-dimesitylboryl)phenyl]ethynyl}-1′,4′-bis[(4-N,N-diphenylamino)phenyl]-[1,1′:4′,1′]terphenyls, which displays a characteristic intramolecular charge transfer transition and is highly emissive both in solutions and solid state. The complexation with fluoride ions induces a large blue shift in fluorescence, enabling ratiometric fluorescence sensing of fluoride. In addition, its prompt response to fluoride ions was also observed even in the solid state.     

Synthesis of substituted quinolines by the electrophilic cyclization of n-(2-alkynyl)anilines

A wide variety of substituted quinolines are readily synthesized under mild reaction conditions by the 6-endo-dig electrophilic cyclization of N-(2-alkynyl)anilines by ICl, I₂, Br₂, PhSeBr, and p-O₂NC₆H₄SCl. The reaction affords 3-halogen-, selenium- and sulfur-containing quinolines in moderate to good yields in the presence of various functional groups. Analogous quinolines bearing a hydrogen in the 3-position have been synthesized by the Hg(OTf)₂-catalyzed ring closure of these same alkynylanilines.     

Uranyl(VI) complexes of [O,N,O,N′]-type diaminobis(phenolate) ligands: Syntheses,structures and extraction studies

The syntheses and crystal structures of four new uranyl complexes with [O,N,O,N′]-type ligands are described. The reaction between uranyl nitrate hexahydrate and the phenolic ligand [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N′,N′-dimethylethylenediamine)], H₂L1 in a 1:2 molar ratio (M to L), yields a uranyl complex with the formula [UO₂(HL1)(NO₃)] · CH₃CN (1). In the presence of a base (triethylamine, one mole per ligand mole) with the same molar ratio, the uranyl complex [UO₂(HL1)₂] (2) is formed. The reaction between uranyl nitrate hexahydrate and the ligand [(N,N-bis(2-hydroxy-3,5-di-t-butylbenzyl)-N′,N′-dimethylethylenediamine)], H₂L2, yields a uranyl complex with the formula [UO₂(HL2)(NO₃)] · 2CH₃CN (3) and the ligand [N-(2-pyridylmethyl)-N,N-bis(2-hydroxy-3,5-dimethylbenzyl)amine], H₂L3, in the presence of a base yields a uranyl complex with the formula [UO₂(HL3)₂] · 2CH₃CN (4). The molecular structures of 1–4 were verified by X-ray crystallography. The complexes 1–4 are zwitter ions with a neutral net charge. Compounds 1 and 3 are rare neutral mononuclear [UO₂(HLn)(NO₃)] complexes with the nitrate bonded in η²-fashion to the uranyl ion. Furthermore, the ability of the ligands H₂L1–H₂L4 to extract the uranyl ion from water to dichloromethane, and the selectivity of extraction with ligands H₂L1, H₃L5 (N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-3-amino-1-propanol), H₂L6 · HCl (N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane · HCl) and H₃L7 · HCl (N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-6-amino-1-hexanol · HCl) under varied chemical conditions were studied. As a result, the most efficient and selective ligand for uranyl ion extraction proved to be H₃L7 · HCl.     

Synthesis of cesium selective pyridyl azocalix[n]arenes

A series of pyridylazo calix[n]arenes (n=4, 6, 8) including the first examples of mixed hetroaryl azocalix(n)arenes have been synthesized by coupling calix[n]arenes with diazonium salts derived from amino pyridines. It has been observed that the coupling reaction of diazonium salt obtained from 3-aminopyridine with calix[n]arene gives tetrakis-, hexakis- and octakis (pyridylazo)calix[n]arenes (n=4,6,8) while those derived from 4-aminopyridine give partially substituted (4-pyridylazo)calix[n]arene analogs. There is no reaction of calix(n)arenes with diazonium salts derived from 2-aminopyridine under identical conditions of experiments. The conformational analysis of synthesized compounds have been ascertained by detailed spectral measurements and single crystal X-ray analysis of 5-(3′-pyridylazo)-25,26,27,28-tetrahydroxycalix[4]arene. A rational explanation for the observed partial and exhaustive coupling reaction in the synthesis of heteroaryl azocalix(n)arenes has been suggested. Preliminary evaluation of synthesized derivatives as molecular receptors for metal ions indicates that they have good potential to function as selective ionic filters for cesium ions.