Functionalized pyridylboronic acids and their Suzuki cross-coupling reactions to yield novel heteroarylpyridines

2-Bromo-5-pyridylboronic acid 2a, 2-chloro-5-pyridylboronic acid 2b, 2-methoxy-5-pyridylboronic acid 2c, and 5-chloro-2-methoxy-4-pyridylboronic acid 4 have been synthesized and shown to undergo palladium-catalyzed cross-coupling reactions with heteroaryl bromides to yield novel heteroarylpyridine derivatives. The X-ray crystal structures of 2a and 2b have been obtained.     

5-Pyrimidylboronic acid and 2-methoxy-5-pyrimidylboronic acid: new heteroarylpyrimidine derivatives via Suzuki cross-coupling reactions

5-Pyrimidylboronic acid and 2-methoxy-5-pyrimidylboronic acid 4 have been synthesised by lithium-halogen exchange reactions on 5-bromopyrimidine and 2-methoxy-5-bromopyrimidine, respectively, followed by reaction with triisopropylborate. Suzuki cross-coupling reactions of 2 and 4 with heteroaryl halides [Na(2)CO(3), Pd(PPh(3))(2)Cl(2), 1,4-dioxane, 95 degrees C] yield heteroarylpyrimidines (heteroaryl = thienyl, quinolyl and pyrimidyl). Two-fold reaction of 2 with 4,6-dichloropyrimidine 12 gave 4,6-bis(5-pyrimidyl)pyrimidine 8(56% yield). Reaction of 4,6-dichloropyrimidine with 2-methoxy-5-pyridylboronic acid gave 4,6-bis(2-methoxy-5-pyridyl)pyrimidine 14 (84% yield). Conversion of into 4,6-bis(2-chloro-5-pyridyl)pyrimidine 15 (63% yield) followed by two-fold Suzuki reaction with 4-tert-butylbenzeneboronic acid gave the penta-arylene derivative 4,6-bis[2-(4-tert-butyl)phenyl-5-pyridyl]pyrimidine 16 (16% yield). Analogous reaction of 12 with 2-methoxy-3-pyridylboronic acid 17 gave 4,6-bis(2-methoxy-3-pyridyl)pyrimidine 18 (64% yield). The X-ray crystal structures of compound 2.0.5H(2)O and compound 18 are reported. The two hydroxyl H atoms in 2 have the usual exo-endo orientation. However, unlike most arylboronic acids, molecule 2 does not form a centrosymmetric hydrogen-bonded dimer. In molecule 18, the pyridine rings form dihedral angles of 39.9 degrees and 22.8 degrees with the central pyrimidine ring.     

Synthesis and electroconductivities of poly(2-methoxy-5-methythio-1,4-phenylene vinylene) and copolymers

Poly(2-methoxy-5-methylthio-1,4-phenylene vinylene), PMTPV, and copolymers containing both unsubstituted or 2,5-dimethoxy-substituted and 2-methoxy-5-methylthio-1,4-phenylene vinylene units were prepared in thin films from their water-soluble, sulfonium salt precursor polymers. Doping of drawn and undrawn films of PMTPV with I₂ vapor led to conductivities of 10^?4–10^?3 S cm^?1, which is significantly lower than those reported for poly(2,5-dimethoxy-1,4-phenylene vinylene). Conductivity of I₂-doped copolymer films ranges from 10^?3–10⁰ S cm^?1 depending on composition.     

Synthesis of 1,5-Dimethoxy-4-naphthol and 2-Allyl-5-methoxy-1,4-Naphthoquinone A New Approach

Convenient syntheses for 1,5-dimethoxy-4-naphthol and 2-allyl-5-methoxy-1,4-naphthoquinone have been developed. A key step in the formation of the title compounds involved methylation or allylation of an intermediate Diels-Alder adduct.     

MEH-PPV型单体[2,5-双(4′-溴-2′,5′-二甲氧基苯基乙烯基)-1-甲氧基-4-(2′-乙基己基氧基)苯]的合成及其发光性能

以对苯二甲醚为原料,经甲酰化和溴代反应合成2,5-二甲氧基-4-溴苯甲醛(2)。以对甲氧基苯酚为原料,经烷基化、氯甲基化和Michaelis-Arbuzov反应合成亚膦酸酯(5);2和5经Horner-Wittig-Emmons反应合成了2,5-双(4′-溴-2′,5′-二甲氧基苯基乙烯基)-1-甲氧基-4-(2′-乙基己基氧基)苯(6),总收率44.7%,其结构经1HNMR,13C NMR和元素分析表征。UV-Vis和荧光光谱(FL)研究表明,6的UV-Vis和FL的λmax分别位于410 nm和479 nm,497 nm,是一种绿光的MEH-PPV型单体。     

Syntheses of 1,4-benzothiazepines and 1,4-benzoxazepines via cyclizations of 1-[2-arylthio(oxy)ethyl]-5-benzotriazolyl-2-pyrrolidinones and 3-benzotriazolyl-2-[2-arylthio(oxy)ethyl]-1-isoindolinones

1-[2-Arylthio(oxy)ethyl]-5-benzotriazolyl-2-pyrrolidinones 6a-e, 12 and 3-benzotriazolyl-2-[2-arylthio(oxy)ethyl]-1-isoindolinones 9a-f, 14 are readily available from reactions of benzotriazole (4), 2-(arylsulfanyl)ethylamines 3, or 2-phenoxyethylamine (11) with 2,5-dimethoxy-2,5-dihydrofuran (5) or 2-formylbenzoic acid (8). Lewis acid mediated cyclizations of 6 and 9 produced novel 1,4-benzothiazepines 7a-e and 10a-f, respectively. Cyclizations of 12 and 14 gave 1,4-benzoxazepines 13 and 15, respectively.     

Protonation and subsequent intramolecular hydrogen bonding as a method to control chain structure and tune luminescence in heteroatomic conjugated polymers

We report the effects of protonation on the structural and spectroscopic properties of 1,4-dimethoxy-2,5-bis(2-pyridyl)benzene (9) and the related AB coploymer poly(2,5-pyridylene-co-1,4-[2,5-bis(2-ethylhexyloxy)]phenylene) (7). X-ray crystallographic analysis of 9, 1,4-dimethoxy-2,5-bis(2-pyridyl)benzene bis(formic acid) complex 10, and 1,4-dimethoxy-2,5-bis(2-pyridinium)benzene bis(tetrafluoroborate salt) (11) establishes that reaction of formic acid with 9 does not form an ionic pyridinium salt in the solid state, rather, the product 10 is a molecular complex with strong hydrogen bonds between each nitrogen atom and the hydroxyl hydrogen in formic acid. In contrast, reaction of 9 with tetrafluoroboric acid leads to the dication salt 11 with significant intramolecular hydrogen bonding (N-H.O-Me) causing planarization of the molecule. The pyridinium and benzene rings in 11 form a dihedral angle of only 3.9 degrees (cf. pyridine-benzene dihedral angles of 35.4 degrees and 31.4 degrees in 9, and 43.8 degrees in 10). Accordingly, there are large red shifts in the optical absorption and emission spectra of 11, compared to 9 and 10. Polymer 7 displays a similar red shift in its absorption and photoluminescence spectra upon treatment with strong acids in neutral solution (e.g. methanesulfonic acid, camphorsulfonic acid, and hydrochloric acid). This is also observed in films of polymer 7 doped with strong acids. Excitation profiles show that emission arises from both protonated and nonprotonated sites in the polymer backbone. The protonation of the pyridine rings in polymer 7, accompanied by intramolecular hydrogen bonding to the oxygen of the adjacent solubilizing alkoxy substituent, provides a novel mechanism for driving the polymer into a near-planar conformation, thereby extending the pi-conjugation, and tuning the absorption and emission profiles. The electroluminescence of a device of configuration ITO/PEDOT/polymer 7/Ca/Al is similarly red-shifted by protonation of the polymer.     

Preparation of 2,3- and 2,5-dihydropyrazine 1,4-dioxides from 2-hydroxyamino-2-methylpropanal oxime and some of their properties

3-Hydroxy-2,3-dihydropyrazine 1,4-dioxide derivatives were obtained by condensation of 2-hydroxyamino-2-methylpropanal oxime with glyoxal, diacetyl, and 1,2-cyclohexanedione in water, and 3-methoxy-2,3-dihydropyrazine 1,4-dioxide was obtained by condensation with diacetyl in methanol. 2,5-Dihydropyrazine 1,4-dioxide is formed when 2-hydroxyamino-2-methylpropanal oxime is heated in a solution of acetone and dilute hydrochloridic acid. The reduction of 3-hydroxy- and 3-methoxy-2,3-dihydropyrazine 1,4-dioxides and 2,5-dihydropyrazine 1,4-dioxide leads to 1,4-dihydroxypiperazines, and the bromination of 3-methoxy-2,3-dihydropyrazine 1,4-dioxide gives 5,6-bis(bromomethyl)-3-methoxy-2,3-dihydropyrazine 1,4-dioxide. 1,4-Dihydroxy-2,5-piperazinedione was obtained by oxidation of 2,5-dihydropyrazine 1,4-dioxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1414–1418, October, 1983.     

New luminescent polymers for leds and LECS

Statistical copolymers 5 containing poly(2-dimethyloctylsilyl-1,4-phenylenevinylene) (DMOS-PPV) and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) have been synthesized using the dehydrohalogenation condensation route. The copolymers show a shift of photoluminescence maxima to longer wavelengths as the proportion of the MEH-PV unit increases. This trend is accompanied by reduced efficiencies and lower turn-on voltages in single layer electroluminescent devices. Light-emitting electrochemical cells (LECs) have been prepared using a blend of DMOS-PPV 1 with poly(ethylene oxide)/lithium triflate and the homopolymer poly[2-methoxy-5-(triethoxymethoxy)-1,4-phenylene vinylene] (MTEM-PPV) 9 with lithium triflate. In comparison with single-layer devices which were fabricated using the homopolymers 1 and poly[2,5-bis(triethoxymethoxy)-1,4-phenylene vinylene] (BTEM-PPV) 10 , the LEC devices showed lower turn-on voltages.     

Alkyl phenols from the wood of Averrhoa carambola

<正>Two alkyl phenols,namely,2,5-dimethoxy-3-undecylphenol(1) and 5-methoxy-3-undecylphenol(2),were isolated together with two known benzoquinones,5-O-methylembelin(3) and 2-dehydroxy-5-O-methylembelin(4) from the wood of Averrhoa carambola.Their structures were elucidated on the basis of spectroscopic methods(1D and 2D NMR).     

Syntheses of some tetralones related to tetracyclines

Syntheses of 5-chloro-8-methoxy-1-tetralone (XIV), 6,8-dimethoxy-1-tetralone (XIX), 2-carbethoxy-6,8-dimethoxy-1-tetralone (VI), 3-(2′-chloro-5′-methoxybenzyl)-6,8-dimethoxy-1-tetralone (III) and 2-carbethoxy-3-(2′-chloro-5′-methoxybenzyl)-6,8-dimethoxy-1-tetralone (IV) are reported. The mode of cyclization with polyphosphoric acid of I and related compounds is described.     

Synthesis of 2,5-diisoxazolyltetrahydrofurans

The synthesis of 2,5-bis(3-bromo-5-isoxazolyl)tetrahydrofuran ( 2 ) and 2,5-bis(3-methoxy-5-isoxazolyl)tetrahydrofuran ( 3 ) have been accomplished in three and four steps respectively. Cis- and trans-isomers have been separated and fully characterized. Differently from synthetic schemes so far utilized for the preparation of the 2,5-diheteroaryltetrahydrofuran analogs, our approach involves the direct synthesis of a key intermediate containing both isoxazole rings and diol function for the final cyclization. Starting from succinic aldehyde, the new 1,7-octadiyne-3,6-diol ( 4 ) was prepared and was submitted to a double cycloaddition with bromonitrile oxide to yield the key intermediate 1,4-bis(3-bromo-5-isoxazolyl)-1,4-butanediol. The methoxy analogs 3 were obtained by methanolysis of the bromo derivatives 2 .     

The Reaction of 2,5-Dimethoxy-2,5-Dihydrofuran with Dichloroketene

2,5-Dimethoxy-2,5-dihydrofuran (DDF) reacts with dichloroketene to give 7,9-dimethoxy-3,3,5,5-tetrachloro-8-oxabicyclo[4,3,0]-noan-2,4-dione (I), and methyl chloro-(2,5-dihydro-5-methoxy-2-furanylidene) acetate (II). The reactions of 2,5-dihydrofuran and 2,5-dimethoxy-tetrahydrofuran with dichloroketene were also-studied for comparison. Compound II was derived from the insertion of a molecule of dichloroketene into the C-O bond of DDF with subsequent dehydrochlorination. Compound I resulted from the cycloaddition of two molecules of dichloroketene to the C=C bond of DDF. A mechanism involving a 1,5-dipolar intermediate is proposed to account for this novel reaction.     

Lewis acid-directed cyclocondensation of piperidone enol ethers with 2-methoxy-4-(N-phenylsulfonyl)-1,4-benzoquinoneimine: a new regioselective synthesis of oxygenated carbolines

Lewis acid-directed cyclocondensations of piperidone enol ethers with 2-methoxy-4-(N-phenylsulfonyl)-1,4-benzoquinoneimine are reported. Benzofurans are obtained with BF3.OEt2 as a promoter, whereas use of excess amounts of TiCl4:Ti(OiPr)4 leads to tetrahydrocarbolines. The latter reactions provide expedient routes to oxygen-substituted tetrahydrocarbolines and carbolines. As applications of this new methodology, the preparations of 1-[3-(dimethylamino)propyl]amino-7-methoxy- and 1-[3-(dimethylamino)propyl]amino-7,8-dimethoxy-5H-pyrido[4,3-b]indoles are described.     

A novel series of copolymers containing 2,5-dicyano-1,4-phenylene-vinylene--synthetic tuning of the HOMO and LUMO energy levels of conjugated polymers

A series of copolymers of 2,5-dicyano-1,4-phenylenevinylene and 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene were synthesized by Wittig reaction. The HOMO and LUMO energy levels of copolymers can be easily tuned by controlling the feed ratio of co-monomers.     

Crystal engineering using anilic acids and dipyridyl compounds through a new supramolecular synthon

The anilic acids, 2,5-dihydroxy-1,4-benzoquinone (1a), 2,5-dibromo-3,6-dihydroxy-1,4-benzoquinone (bromanilic acid; 1b), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid; 1c), and 2,5-dicyano-3,6-dihydroxy-1,4-benzoquinone (cyananilic acid; 1d), were cocrystallized with rigid organic ligands containing two pyridine rings, 2,4-bipyridine (2a), 4,4'-bipyridine (2b), 1,2-bis(2-pyridyl)ethylene (3a), 1,2-bis(4-pyridyl)ethylene (3b), 2,2'-dipyridylacetylene (4a), 3,3'-dipyridylacetylene (4b), and 4,4'-dipyridylacetylene (4c). Fourteen complexes 5-18 were obtained as single crystals, and their crystal structures were successfully determined by X-ray analysis. All complexes except those with 2a are 1:1 and are composed of an infinite linear or zigzag tape structure, the formation of which is ascribed to intermolecular O-H...N, N(+)-H...O, or N(+)-H...O(-) hydrogen bonds or a combination of these between the anilic acids and the dipyridyl compounds. In the complexes 5 and 6, no infinite tape structure is observed although the molecular units connected by a similar hydrogen-bonding pattern are formed. For the 1:1 complexes, we have found two types of stacking arrangements, segregated stacks (7, 9, 12-15, 18) and alternated ones (8, 10, 11, 16, 17). In the complexes of 1c with the series of dipyridylacetylenes 4 (14, 15, 17), the neutral, dication, and monocaction states are formed depending on the nitrogen positions, which can be attributed to the different basicity of the pyridyl groups.     

Approaches to phenazine-derived N-isosteres of anthracyclinones

1-Hydroxyphenazine 5,10-dioxide showed antitumor properties against mouse leukemia P388. It also participated in biochemical mechanisms of quinoid antitumor agents, as indicated by inhibition of radiolabeled DNA-RNA precursors in cultured leukemia L1210 cells and by stimulation of oxygen consumption in mammalian microsomes. This suggests that the isosteric di-N-oxide system may be a biologically active substitute for 1,4-quinone, and that di-N-oxides of tetrahydrobenzo[b]phenazines can be explored as anthracyclinone N-isosteres. As potential synthetic intermediates, 7,8,9,10-tetrahydro-6,11-dihydroxybenzo[b]-phenazines have been prepared by 1) Diels-Alder addition of phenazine-1,4-quinone and 1-methoxy-3-(trimethylsilyloxy)-1,3-butadiene to give isolable but labile adducts and 2) condensation of 6,7-diamino-1,2,3,4-tetrahydro-2-hydroxy-5,8-dimethoxy-2-naphthoic acid with 3-methoxy-1,2-quinone. Attempts at N-oxidation gave instead oxidation of the 6,11-hydroquinone ring to quinone, regardless of hydroxyl protection. Despite previous literature indications, we have been unable to synthesize the 1,4-dihydroxyphenazine 5,10-dioxide system. We conclude that this hydroxyl substitution pattern (1,4) in an adjacent ring must be avoided in the redesign of anthracyclinone isosteres that have di N-oxide in place of quinone.     

A 5-methylthiopenicillin analog and its transformation to novel bicyclic β-lactams

Reaction of methoxyacetyl chloride with 2-methylthio-2-thiazoline resulted in the stereoselective production of one isomer of 6-methoxy-5-methylthiopenam which underwent rearrangement to 6-methoxy-7-methylthio-5-oxo-2,3,4,5-tetrahydro-1,4-thiazepine when treated with trifluoroacetic acid. Subsequent thioamidation and alkylation with methyl iodide provided 5,7-bismethylthio-6-methoxy-2,3-dihydro-1,4-thiazepine which reacted with methoxyacetyl chloride and triethylamine to give a novel 1,4-thiazabicyclo[5.2.0]non-5-ene. Other substituted bicyclic β-lactams of similar structure have also been synthesized.     

Protogenkwanin,a new flavonoid from equisetum arvense L

From the fertile sprouts of Equisetum arvense L. have been isolated protogenkwanin 4'-glucoside and gossypitrin. The structure of protogenkwanin as 5-hydroxy-2-(1,4-dlhydroxy-2,5-cyclohexadienyl)-7-methoxy-4-chromenon is proved on the basis of chemical and physical evidence. It is demonstrated that articulatin a thiamine decomposing substance, from E. arvense, is identical with the known flavonol glycoside gossypitrin (= gossypetin-7-glucoside). The synthesis of 2,5-dihydroxy-2-(4 hydroxyphenyl)-7-methoxy-4-chromanon is reported.     

Synthesis of hydroxy-6H-benzofuro[3,2-c] [1]benzopyran-6-ones

The Micheal addition of ethyl 2-methoxy-, 2,4-dimethoxy- and 2,5-dimethoxybenzoylacetates with benzoquinone leads to ethyl 2-(rnethoxy or dimethoxy phenyl)-5-hydroxybenzofuran 3-carboxylates. Treatment of the henzofuran derivatives with anhydrous pyridine hydrochloride at 190–195° leads to hydroxy-6H-henzofuro[3,2-c] [1]benzopyran-6-ones.