Preparative fluorous mixture synthesis of diazonium-functionalized oligo(phenylene vinylene)s

[structure: see text] A series of building blocks for the synthesis of oligo(phenylene vinylene)s (OPVs) and hybrid oligomers were prepared, and alternating Heck coupling and Horner-Wadswoth-Emmons (HWE) reactions were used to couple the building blocks. Model studies were carried out to optimize the reaction strategies. The products were made to bear aryl diazonium functionalities that allow them to be used as surface grafting moieties in hybrid silicon/molecule assemblies. A library of OPV and hybrid oligomer tetramers was synthesized using fluorous mixture synthesis (FMS). The fluorous tags, which are secondary amines bearing different numbers of fluorine atoms, were synthesized and used as phase tags in mixture synthesis. The tags and substrates were anchored together by triazene linkages. The mixture synthesis was monitored by analytical HPLC on a fluorous column, and isolation of final OPV and hybrid oligomer tetramers was achieved by preparative HPLC. At the end of the FMS, after demixing, the tagged products were detagged by cleaving the triazene linkage and generating a series of aryl diazonium compounds. The fluorous tags could be recovered and reused. The NMR spectra of the 1-aryl-3,3-dialkyltriazenes are discussed.     

Regioselective arylation of 3-bromopyridine

The addition of aryl Grignard reagents to the 1-phenoxycarbonyl salt of 3-bromopyridine affords 2-aryl-5-bromo-1-phenoxycarbonyl-1,2-dihydropyridines and 4-aryl-3-bromo-1-phenoxycarbonyl-1,4-dihydropyridines. The crude dihydropyridines were aromatized with o-chloranil in refluxing toluene to give 4- and 6-aryl-3-bromopyridines. The regioselectivity of this two-step process, 6- vs. 4-substitution, was examined and found to be dependent upon the structure of the Grignard reagent. Unhindered aryl Grignard reagents, e.g., phenyl and 2-naphthyl, gave mainly 6-aryl-3-bromopyridines (49-52%) along with 9% of the 4-substituted isomer and less than 4% of the 2-aryl-3-bromopyridine. Hindered aryl Grignard reagents, e.g., o-tolyl and 1-naphthyl, are less regioselective. When a catalytic amount of cuprous iodide is present during the Grignard reaction, nearly exclusive 1,4-addition results. The crude 4-aryl-3-bromo-1,4-dihydropyridines were aromatized with p-chloranil to provide 4-aryl-3-bromopyridines in good yield and high isomeric purity. The sequential use of the cuprous iodide-catalyzed Grignard reaction and the “normal” Grignard reaction provided a regiospeci-fic synthesis of 3-bromo-6-(p-methoxyphenyl)-4-phenylpyridine from 3-bromopyridine.     

Synthesis of oligonucleotides possessing versatile probes for PET labelling and their rapid ligand-free click reaction

We synthesised aryl acetylene derivatives as versatile probes for labelling of oligonucleotides. RNA oligomers bearing an aryl acetylene molecule rapidly reacted with benzylazide derivatives under ligand-free click reaction conditions.     

On the reaction of 5-aminopyrimidine with diazonium salts

The reaction of 5-aminopyrimidine with benzenediazonium chloride, p-methylbenzenediazonium chloride and p-bromobenzenediazonium chloride is described. The reaction leads to a mixture of compounds, i.e. 1-aryl-3-(pyrimidin-5-yl)triazene ( 6 ), 5-amino-4-aryl-6-arylazopyrimidine ( 7 ) and 4-aryl-6-arylazo-5-hydroxypyrimidine ( 8 ). The yields are found to be strongly dependent on the substituent present in the diazonium salt. Attempts to rearrange 1-(p-bromophenyl)-3-(pyrimidin-5-yl)triazene ( 6c ) under basic and acidic conditions into a 1,2,3-triazole derivative failed.     

Synthesis of fluoro‐substituted silole‐containing conjugated materials

2,5‐Dihydroxyboryl‐1,1‐dimethyl‐3,4‐bis(3‐fluorophenyl)‐silole ( 2a ) was prepared in 40% overall yield by reaction between 3‐fluorophenyl‐acetylene and dichlorodimethylsilane to yield bis[2(3‐fluorophenyl)ethynyl]dimethylsilane ( 1a ), which subsequently undergoes a reductive cyclization reaction using an excess of lithium naphthalenide. The fluoro substituted silole was applied as a co‐monomer in the Suzuki polycondensation reaction with 2,7‐dibromo‐9,9‐dioctyl‐fluorene. An oligomer ( 3a ) with a degree of polymerization of 6 was prepared and compared with an oligomer without fluoro substitution on the silole ( 3b ), with a degree of polymerization of 4. The new oligomers were spin coated onto glass slides and showed weak green photoluminescence (PL) in the solid state. Cyclic voltammetry, visible absorption spectroscopy, and density functional theory calculations showed that the fluoro substituents were sufficiently electron withdrawing to lower both the highest occupied molecular orbital and the lowest unoccupied molecular orbital in the oligomer. Two further alternating co‐oligomers were prepared from 2,5‐dihydroxyboryl‐1,1‐dimethyl‐3,4‐bis(phenyl)‐silole ( 2b ) and 1,3‐dibromo‐5‐fluoro‐benzene ( 4a ) or 1,3‐dibromobenzene ( 4b ). These oligomers both had degrees of polymerization of 8 and showed green PL in the solid state. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5116–5125, 2009     

Pd-catalyzed C-H activation/C-N bond formation: a new route to 1-aryl-1H-benzotriazoles

A method for the C-H activation of aryl triazene compounds followed by intramolecular amination is described. It involves the use of a catalytic amount of Pd(OAc)(2) that efficiently effects the cyclization to provide 1-aryl-1H-benzotriazoles at moderate temperature.     

Synthesis of 9-alkylidene-9H-fluorenes by a novel, palladium-catalyzed cascade reaction of aryl halides and 1-aryl-1-alkynes.

In the presence of a palladium catalyst and NaOAc, aryl iodides react with 1-aryl-1-alkynes to afford 9-alkylidene-9H-fluorenes in good yields. The products from this reaction are highly dependent on the base employed. This process appears to involve (1) oxidative addition of the aryl iodide to Pd(0), (2) alkyne insertion, (3) rearrangement of the resulting vinylic palladium intermediate to an arylpalladium species, and (4) aryl-aryl coupling with simultaneous regeneration of the Pd(0) catalyst. Consistent with this mechanism is the fact that 9-alkylidene-9H-fluorenes can also be prepared by the Pd-catalyzed rearrangement of 1,1-diaryl-2-iodo-1-alkenes.     

Alkylation of aryl 3-oxopropanedithioate and 3-amino-1-aryl-3-thioxo-1-propanones as an effective tool for the construction of differently substituted thiophenes and annulated thiophenes

The alkylation of aryl 3-oxopropanedithioate with α-haloketones under different reaction conditions afforded substituted aryl[2-(methylsulfanyl)-4-phenyl-3-thienyl]methanones and [3-aryl-5-(methylsulfanyl)-2-thienyl](phenyl)methanones. The same strategy was extended to 3-amino-1-aryl-3-thioxo-1-propanones to afford aryl[2-amino-4-phenyl-3-thienyl]methanones and ethyl 3-phenyl-5-piperidino-2-thiophene carboxylate.     

Facile dearomatizing radical arylation of furan and thiophene

In the presence of catalytic diphenyl diselenide, reduced in situ to benzeneselenol, tributyltin hydride and V-70 promote the addition of aryl iodides to furan and thiophene. The adduct radicals are trapped by the selenol to give the 2-aryl-2,3-dihydro and 2-aryl-2,5-dihydro heterocyclic products. When the iodide is an o-iodophenol, a cyclization follows the radical addition and provides bridged bicyclic acetals. [reaction: see text]     

Meerwein arylation with 3-fluorobutenone

3-Fluorobutenone (7) reacts with aryl triazenes in the presence of zinc iodide to give 4-aryl-3-fluoro-3-iodo-2-butanones (9a-9f) in moderate yields. The products arise from a free radical process that terminated by iodination of an alkyl radical. The process yields unusual geminal iodo-fluoro compounds.     

Preparation and reaction of 2-aryl-3-silyl-1,3-butadiene

[reaction: see text] A conjugated pi-electron compound, 2-aryl-3-silyl-1,3-butadiene, was easily prepared from 1-benzyloxy-3-silyl-2-propyne, bis(iodozincio)methane, and an aryl halide in the presence of nickel catalyst. A subsequent cross-coupling reaction of the product with another aryl halide gave an unsymmetrical 2,3-diaryl-1,3-butadiene efficiently.     

Synthesis of heterocycles. Part VI. Synthesis and antimicrobial activity of some 4-amino-5-aryl-1,2,4-triazole-3-thiones and their derivatives

4-Amino-5-aryi-1,2,4-triazole-3-thiones I react with acid chlorides to yield 4-acylamino-5-aryl-1,2,4-triazole-3-thiones II. Compounds I also react with methylene iodide, chloroacetonitrile and methyl bromoacetate to give bis-(4-amino-5-aryl-1,2,4-triazol-3-ylthio)methanes III, 4-amino-5-aryl-3-cyanomethylthio-1,2,4-triazoles IV and 4-amino-5-aryl-3-carbomethoxymethylthio-1,2,4-triazoles V, respectively. Compounds V react with hydrazine hydrate to give the corresponding acid hydrazides VI which in turn condenses with acid chlorides and aldehydes to afford respectively 1-[(4-amino-5-aryl-1,2,4-triazol-3-ylthio)acetyl]-2-aroylhydrazines VII and aryl methylene (4-amino-5-aryl-1,2,4-triazol-3-ylthio)acethydrazones VIII. The antimicrobial activities of the above compounds were screened against different strains of bacteria and fungi.     

Poly(aryl ether)s containing o‐terphenyl subunits. II. Random poly(ether sulfone)s

The synthesis of a new A₂X‐type difluoride monomer, N‐2‐pyridyl‐4′,4″‐bis‐(4‐fluorobenzenesulfonyl)‐o‐terphenyl‐3,6‐dimethyl‐4,5‐dicarboxylic imide ( 3 ), is described. The monomer 3 was incorporated into a series of copoly(aryl ether sulfone)s by polymerization of 4,4′‐isopropylidenediphenol and 4,4′‐difluorophenylsulfone. The incorporation of monomer 3 had an observable effect on both the glass‐transition temperature of poly(aryl ether sulfone)s and the tendency for macrocyclic oligomers to form during polymerization. Replacement of the pyridyl imide group via a transimidization reaction with propargyl amine proceeded quantitatively and without polymer degradation. The acetylene containing copoly(aryl ether sulfone) could be crosslinked by simple thermal treatment, resulting in an increase in the glass‐transition temperature and solvent resistance. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 9–17, 2000     

5-Amino-4,5-dihydroisoxazoles. Part I. 5-Amino-3-aryl-4-methylene-4,5-dihydroisoxazoles and 4-aminomethyl-3-arylisoxazoles from 5-amino-4-aminomethyl-3-aryl-4,5-dihydroisoxazoles

5-Amino-4-aminomethyl-3-aryl-4,5-dihydroisoxazoles 2 were obtained by cycloaddition of nitrile oxides to 1,3-diaminopropenes 1. On reaction with methyl iodide the corresponding 4-(quaternary)-ammoniomethyl iodides 3 were formed. These compounds, on reaction with bases, afforded 5-amino-3-aryl-4-methylene-4,5-dihydroisoxazoles 4. The acid-catalyzed deamination of compounds 2 afforded 4-aminomethyl-3-arylisoxa-zoles 5 and 3-arylisoxazoles as retro-Mannich products. The deamination of 2 to yield 5 was also obtained by base catalysis.     

Copper-free palladium-catalyzed sonogashira-type coupling of aryl halides and 1-aryl-2-(trimethylsilyl)acetylenes

A one-pot procedure for the direct coupling of 1-aryl-2-trimethylsilylacetylenes with aryl halides to give diaryl acetylenes is reported. The procedure does not involve the use of copper(I) iodide. Improvement in reaction yields has been obtained by replacing conventional oil bath heating with the use of microwave dielectric heating.     

Synthesis of 9-alkylidene-9H-fluorenes by a novel palladium-catalyzed rearrangement

In the presence of a palladium catalyst and NaOAc, aryl iodides react with 1-aryl-1-alkynes to afford 9-alkylidene-9H-fluorenes in good yields. This process appears to involve (1) oxidative addition of the aryl iodide to Pd(0), (2) alkyne insertion, (3) rearrangement of the resulting vinylic palladium intermediate to an arylpalladium species, and (4) aryl-aryl coupling with simultaneous regeneration of the Pd(0) catalyst.     

Exploratory chemistry of 3-aroylformamido-4-aryl-1,2,5-thiadiazoles

Apart from the previous report, the reaction of 3-(4-nitrobenzoylformamido)-4-(4-nitrophenyl)-1,2,5-thiadiazole ( 2a ) with m-chloroperbenzoic acid in chloroform at room temperature did not proceed, whereas at reflux temperature the same reaction gave 4-nitrobenzoic acid ( 5 ) (86%) and a minute amount of a mixture of 4-nitrobenzoylformamide ( 6 ) and 3-amino-4-(4-nitrophenyl)-1,2,5-thiadiazole ( 7a ). On the other hand the same reaction in a mixture of ethanol and chloroform (1:4) at room temperature gave 3-ethoxycarbamoyl-4-(4-nitrophenyl)-1,2,5-thiadiazole ( 8a ) (24%) as an isolable product. When 3-aroylformamido-4-aryl-1,2,5-thiadiazoles 2 in tetrahydrofuran were treated with various alkoxides in the corresponding alcohols at room temperature, 3-amino-4-aryl- 7 , 3-alkoxycarbamoyl-4-aryl- 8 , and 3-aryl-4-(aryl)(hydroxy)acetamido-1,2,5-thiadiazoles 9 were isolated. The ratios of which were dependent on the kind of bases and the solvent employed. Selected compounds 2 were allowed to react with phosphorus pentasulfide in the presence of pyridine at reflux to give 3-aryl-4-arylacetarnido-1,2,5-thiadiazoles 17 (55–64%), which were also produced by the reaction of 2 with either Lawesson's reagent or hydrogen sulfide gas in the presence of pyridine at reflux.     

N-Arylation of 4-fluoro-5-trimethylsilyl-1H-pyrazole

The 1,3-dipolar cycloaddition reaction of fluoro(trimethylsilyl)acetylene prepared in situ with an excess of diazomethane smoothly proceeded to give the corresponding 4-fluoro-5-trimethylsilyl-1H-pyrazole in 84% yield. The copper iodide-catalyzed N-arylation of the fluorinated pyrazole with a variety of aryl iodides afforded N-aryl-4-fluoropyrazoles as desilylation products in good to excellent yields.     

Formation of benzylamines from triazene compounds via a 1,2-proton shift

A new approach to benzylamines using triazene compounds has been developed that is facilitated by the lithiation of aryltriazenes followed by treatment with an electrophile. The regioselectivity of the reaction can be controlled by means of the substituents in the aryl group. The reaction contains the following steps: intramolecular carbon-carbon bond formation involving lithiation of an alkyl group on a 3-nitrogen atom; a 1,2-proton shift; and the subsequent release of nitrogen gas. Through the use of a deuterated triazene, we were able to determine that the reaction proceeds through a 1,2-proton shift.     

FTIR investigation of cross-linking and isomerization reactions of acetylene-terminated polyimide and polyisoimide oligomers

The interrelationship between the cross-linking and isoimide-imide isomerization reactions of oligomeric isoimides and imides was investigated using FTIR spectroscopy. It was found that cross-linking of the acetylene units of Thermid IP-600 retarded the local rearrangement of the isoimide to imide conversion of Thermid IP-600 compared with an aniline-terminated analog, decreasing the rate constant by a factor of about 2. The increased flexibility of both the isoimide (Thermid IP-600) and imide (Thermid FA-700) oligomers increased the cross-linking rate of the acetylene end groups by a factor of 4 and 2, respectively, over that of the more rigid imide oligomer (MC-600). With increasing conversion of the isoimide to imide linkages in Thermid IP-600, the kinetic parameters, E_α and in A, for the cross-linking reaction of this oligomer became the same as those for the oligomeric imide, Thermid MC-600. © 1994 John Wiley & Sons, Inc.