Photoinduced step-growth polymerization of thieno[3,4-b] thiophene derivatives. The substitution effect on the reactivity and electrochemical properties

We herein report photoinduced step-growth polymerization of highly conjugated 2,5-dithiophenyl (thieno[3,4-b] thiophene) (TTs) derivatives possessing 4-cyanophenyl or 4-methoxyphenyl or 3-(4-fluorophenyl) groups substituted at the terminal position. Upon irradiation at 350 nm, the excited state of these molecules forms exciplex with diphenyliodonium hexafluorophosphate (DPI) that undergoes electron transfer reaction forming radical cations. Successive proton release and radical coupling reactions yield corresponding oligothienothiophenes with overall yields varying between 19–74%. Structural and molecular weight characteristics of the oligomers thus formed were investigated by Ultraviolet, fluorescence, NMR (Nuclear Magnetic Resonance) and infrared (IR) spectroscopic methods, and GPC (Gel Permeation Chromatography), respectively. The effect of substitution and dithiophene side groups on the reactivity of the monomer and band gap of the oligomers formed was evaluated by using cyclic voltammetry.     

Synthesis and Transformations of 2,4,4,7-Tetramethyl-4-silanaphtho[3,2-b]thiophen-9-one

The catalytic dehydrocyclization of dimethyl(5-methyl-2-thienyl)(2,4-dimethylphenyl)silane accompanied by a skeletal rearrangement gives 2,4,4,7-tetramethyl-4,9-dihydro-4-silanaphtho[3,2-b]thiophene, which was oxidized to 2,4,4,7-tetramethyl-4-silanaphtho[3,2-b]thiophen-9-one, whose structure was solved by X-ray diffraction structural analysis. Various chemical transformations of the ketone synthesized were performed including radical bromination by bromosuccinimide, condensation with furfural in the presence of KOH, reduction by LiAlH₄, and nitration by acetyl nitrate.     

The synthesis of 5,10-dihydro- and 2,3,5,10-tetrahydrothiazolo-[3,2-b] [2,4]benzodiazepines, 1,2,3,4,7,12-hexahydrobenzothiazolo-[3,2-b] [2,4] benzodiazepine,and 9,14-dihydro-6H-[1]benzothiopyrano-[4′,3′:4,5]thiazolo[3,2-b] [2,4] benzodiazepine via 1,2,4,5-Tetrahydro-3H-2,4-benzodiazepine-3-thione

Catalytic reductive scission of phthalazine (II) utilizing a two-stage palladium-Raney nickel procedure afforded o-xylene-α,α′-diamine (III) in 97% yield. Treatment of III with carbon disulfide gave [o-(aminomethyl)benzyl]dithiocarbamic acid (IV), which upon thermal cyclization furnished 1,2,4,5-tetrahydro-3H-2,4-benzodiazepine-3-thione (V). Reaction of V with 1,2-dibromoethane, chloro-2-propanone, ethyl 2-chloroacetoacetate, ethyl chloroacetate, and ethyl 2-bromohexanoate gave 2,3,5,10-tetrahydrothiazolo[3,2-b][2,4]benzodiazepine (VII) and substituted 5,10-dihydrothiazolo[3,2-b][2,4]benzodiazepines (Villa and b, IX, and X), respectively. Condensation of V with 2-chlorocyclohexanone and 3-bromothiochroman-4-one afforded 1,2,3,4,7,12-hexahydrobenzothiazolo[3,2-b][2,4]benzodiazepine (XII) and 9,14-dihydro-6H-[1]benzothiopyrano[4′,3′:4,5]thiazolo[3,2-b][2,4]benzodiazepine(XIll). None of the compounds possessed appreciable biological activity.     

Reactions of 4,4,9-trimethyl-4,9-dihydro-4-silanaphtho[3,2-b]thiophen-9-one with nucleophilic and electrophilic reagents

We have studied the reaction of 4,4,9-trimethyl-4,9-dihydro-4-silanaphtho[3,2-b]-thiophen-9-one with organometallic compounds, lithium aluminum hydride, sodium borohydride, aniline, and acetyl nitrate. We have obtained secondary and tertiary dihydrosilanaphtho[3,2-b]thiophen-9-ols and 9-phenyliminodihydrosilanaphtho[3,2-b]thiophene. We have established that nitration of dihydrosilanaphthothiophen-9-one occurs at the position of the thiophene moiety.Russian University of International Friendship, Moscow 117923. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 621–625, May, 1998.     

Thieno[3,2-b]pyrrolo donor fused with benzothiadiazolo, benzoselenadiazolo and quinoxalino acceptors: synthesis, characterization, and molecular properties

Nitrogen-bridged donor-acceptor multifused dithienopyrrolobenzothiadiazole (DTPBT) and dibenzothiadiazolopyrrolothiophene (DBTPT) were successfully synthesized by intramolecular Cadogan annulation. The electron-deficient benzothiadiazole unit in DTPBT can be converted to benzoselenadiazole and quinoxaline moieties through reduction/cyclization to generate dithienopyrrolobenzoselenadiazole (DTPBSe) and dithienopyrroloquinoxaline (DTPQX), respectively. The nitrogen atoms function as the bridges for covalent planarization to induce intermolecular interaction and intramolecular charge transfer.     

5α-androstano [3,2-b]pyridines, 5α-androstano[17,16-b]pyridines and androst-4 and 5-eno[17,16-b]pyridines

A new synthesis of 5α-androstano[3,2-b]pyridin-17β-ol acetate (VIa) and 17-methyl-5α-androstano[3,2-b]pyridin-17β-ol (VIb), first reported by Shimizu, Ohta, Ueno, and Takegoshi, was achieved. The analogous 5α - androstano[17,16-b]pyridin-3β-ol (XII), 5α-androstano[17,16-b]pyridin-3-one (XIVa), and androst-4-eno[17,16-b]pyridin-3-one (XIVb) were also prepared. An illustration of the method follows. Condensation of 3β-hydroxy-5α-androstan-17-one (VIIa) with 3-(2-furyl)acrolein afforded 16-[3-(2-furyl)-2-propenylidene]-3β-hydroxy-5α-androstan-17-one (VIIIa), the oxime (IXa) of which was thermally cyclized to 5α-androstano[17,16-b]-6′-(2-furyl)pyridin-3β-ol (Xa). 3β-Hydroxy-5α-androstano[17,16-b]pyridine-6′-carboxylic acid (XI) was obtained by ozonolysis of Xa. Thermal decarboxylation of XI gave XII. Cinnamaldehyde was used in place of 3-(2-furyl)acrolein to give the corresponding phenylpyridines.     

Furopyridines. IX. Syntheses and properties of 3-ethoxy derivatives of furo[2,3-b]-, furo[3,2-b]-, furo[2,3-c]- and furo[3,2-c]pyridine

Reaction of ethyl 3-ethoxycarbonylmethoxyfuropyridine-2-carboxylates 2a-2d with sodium ethoxide afforded 3-ethoxy derivatives 3a-3d which converted to 3-ethoxyfuropyridines 5a-5d by hydrolysis and decarboxylation of the ester group. Vilsmeier reaction of 5a and 5b gave 2-formyl-3-ethoxy derivatives 6a and 6b and 2-formyl-3-chloro derivatives 7a and 7b , while 5c and 5d did not give any formyl compound. Bromination of 3-ethoxyfuropyridines with 1 equivalent mole of bromine gave 2-bromo-3-ethoxyfuropyridines 9a-9d , whereas reaction with 3 equivalents of bromine yielded 2,2-dibromo-3,3-diethoxy-2,3-dihydrofuropyridines ( 10a and 10b ) and/or 2-bromo-3,3-diethoxy-2,3-dihydrofuropyridines 11b , 11c and 11d . Treatment of compounds 5a-5d with n-butyllithium in hexane-tetrahydrofuran at ?70° and subsequent addition of N,N-dimethylformamide yielded 2-formyl derivatives 6a-6d .     

Nitration of dithieno[3,2-b:3′,2′-d]pyridine and dithieno[3,2-b:3′,4′-d]pyridine

Nitration of dithieno[3,2-b:3′,2′-d]pyridine ( 4 ) and dithieno[3,2-b:3′,4′-d]pyridine ( 5 ) has been studied. Nitration of 4 occurred in both positions of the C ring, while 5 was predominantly substituted on the 3,4-fused ring. The structures of the nitro derivatives were proven by extensive use of ¹H and ¹³C nmr spectroscopy.     

Furopyridines. XV . Synthesis and properties of ethyl 2-(3-furo[2,3-b]-, -[3,2-b]-, -[2,3-c]- and -[3,2-c]pyridyl)acetate

Ethyl 2-(3-furopyridyl)acetates 10a-d were synthesized from furopyridin-3(2H)-ones 4a-d by the Wittig-Horner reaction with diethyl cyanomethylphosphonate, hydrolysis and the subsequent esterification. Reaction of compounds 10a-d with lithium diisopropylamide (IDA) gave the corresponding methylene-lithiated intermediate, and the subsequent reaction with benzaldehyde, acetone and iodomethane afforded the methylene-alkylated product respectively, while N,N-dimethylacetamide did not give any reaction product. The 2-position of 10a, b and d is alkylated by the lithiation with excess of LDA and the successive reaction with an electrophile.     

Synthesis, structures, and photochromic properties of 2-methylthieno[3,2-b][1]benzothiophen-3-ylfulgide

The novel heterocyclic fulgide, 3-(1-methylethylidene)-4-[1-(2-methylthieno[3,2-b]-[1]benzothiophen-3-yl)ethylidene]dihydrofuran-2,5-dione, was obtained and isolated as a Z-isomer. Its structure was confirmed by electronic absorption spectroscopy, ¹H NMR spectroscopy, and X-ray diffraction analysis. The novel thienothiophene fulgide is photochromic in both solutions and the crystalline state. Its colored cyclic form resists photodegradation and is thermally stable. When benzothiophene is annulated with the thienyl fragment, the long-wavelength absorption peak of the cyclic isomer of the novel fulgide experiences a bathochromic shift compared to the earlier described 3-thienylfulgide. The TD B3LYP/6-311G**-calculated spectroscopic characteristics of the fulgide isomers suggest the formation of their photostationary mixture under irradiation with λ = 365 nm. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2318–2324, December, 2007.     

One-step synthesis of 5-acetyl-2-amino-4-aryl-3-cyano-4H-pyrano[3,2-b]indoles. Molecular and crystal structure of 5-acetyl-2-amino-4-(4"-chloro-3"-nitrophenyl)-3-cyano-4H-pyrano[3,2-b]indole

A one-step procedure was developed for the synthesis of 5-acetyl-2-amino-4-aryl-3-cyano-4H-pyrano[3,2-b]indoles involving the three-component reaction of 1-acetylindol-3(2H)-one with aromatic aldehydes and malononitrile in ethanol in the presence of triethylamine as the catalyst. The structure of 5-acetyl-2-amino-4-(4"-chloro-3"-nitrophenyl)-3-cyano-4H-pyrano[3,2-b]indole was established by X-ray diffraction analysis.     

Additive assisted hydrothermal synthesis,characterization and optical properties of one dimensional DyPO4:Ce3+ nanostructures

One dimensional nanostructures of cerium doped dysprosium phosphate (DyPO₄:Ce³⁺) were synthesized via hydrothermal route in the presence of different surfactants [sodium dodecyl sulfate (SDS), dodecyl sulfosuccinate (DSS), polyvinyl pyrollidone (PVP)] and solvent [ethylene glycol and water]. The prepared nanostructures were characterized by Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-VIS-NIR absorption spectrophotometer and photoluminescence (PL) studies. The PXRD and FTIR results indicate purity, good crystallinity and effective doping of Ce³⁺ in nanostructures. SEM and TEM micrographs display nanorods, nanowires and nanobundles like morphology of DyPO₄:Ce³⁺. Energy-dispersive X-ray spectra (EDS) of DyPO₄:Ce³⁺nanostructures confirm the presence of dopant. UV-VIS-NIR absorption spectra of prepared compounds are used to calculate band gap and explore their optical properties. Luminescent properties of DyPO₄:Ce³⁺ was studied by using PL emission spectra. The effect of additives and solvents on the uniformity, morphology and optical properties of the nanostructures were studied in detail.     

Schiff base substitute polyphenol and its metal complexes derived from o‐vanillin with 2,3‐diaminopyridine: synthesis,characterization, thermal,and conductivity properties

Poly‐2,3‐bis[(2‐hydroxy‐3‐methoxyphenyl)methylene]diamino pyridine (PHMPMDAP) that a new Schiff base polymer has been synthesized and characterized by spectroscopy, elemental, and thermal analyses techniques. This azomethine polymer was found to form complexes readily with Cu(II), Zn(II), Co(II), Pb(II), and Fe(II). From IR and UV‐Vis studies, the phenolic oxygen and imine nitrogen of the ligand were found to be the coordination sites. Thermogravimetric analysis (TGA) data indicate the polymer to be more stable than the monomer. The structure of the polymer obtained was confirmed by FT‐IR, UV‐Vis, ¹³C‐NMR, and ¹H‐NMR. Characterization was undertaken by TGA, size exclusion chromatography (SEC), and solubility tests. Also, electrical conductivities of PHMPMDAP and polymer–metal complexes are measured by four probe technique. Copyright © 2008 John Wiley & Sons, Ltd.     

From model compounds to extended pi-conjugated systems: synthesis and properties of dithieno[3,2-b:2',3'-d]phospholes

To explore their suitability for applications in molecular optoelectronics and as sensory materials, novel dithieno[3,2-b:2',3'-d]phospholes have been synthesized and their reactivity and properties investigated. An efficient two-step synthesis allowed for a modular assembly of differently functionalized compounds. The dithieno[3,2-b:2',3'-d]phosphole system exhibits extraordinary optoelectronic properties with respect to wavelength, intensity, and tunability. Owing to the nucleophilic nature of the central phosphorus atom, its significant electronic influence on the conjugated pi system can be altered selectively by chemically facile modifications such as oxidation or complexation with Lewis acids or transition metals. All the dithienophosphole species presented show very strong blue photoluminescence with excellent quantum yield efficiencies supporting their potential utility as blue-light emitting components in organic light emitting diodes (OLEDs). Furthermore, depending on the electronic nature of the phosphorus center, the materials exhibit distinctive optoelectronic properties suggesting that the dithieno[3,2-b:2',3'-d]phosphole system may be useful as sensory material. Theoretical calculations, including time-dependent DFT methods, revealed the excellent predictability of the structures and optoelectronic properties of the functionalized dithienophospholes allowing the design of future dithieno[3,2-b:2',3'-d]phosphole-based materials to be "stream-lined". By using tin-functionalized dithienophosphole monomers, a strategy, which involves Stille coupling, towards extended pi-conjugated materials with significantly redshifted optoelectronic properties is also presented.     

Furopyridines. XII . Reaction of 3-bromo, 2-phenylthio and 2-phenylthio-3-bromo derivatives of furo[2,3-b]-, furo[3,2-b]-, furo[2,3-c]- and furo[3,2-c]pyridine with several alkyllithiums

This paper describes reactions of 3-bromo- 1a-d , 2-phenylthio- 5a-d and 2-phenylthio-3-bromofuropyridines 6a-d with n-butyl-, t-butyl- and methyllithium and lithioacetonitrile. Lithiation of compounds 1a-d with n-butyl- or methyllithium gave the parent furopyridines 2a-d and o-ethynylpyridinols 3a-d. Reaction of compounds 5a-d with methyllithium afforded o-(phenylthioethynyl)pyridinols 7a-d , which were also yielded by reaction of compounds 6a-d with t-butyl- or methyllithium. The phenylthio group in compounds 7a-d were substituted with t-butyl group by the reaction with excess t-butyllithium. In contrast, 2-phenylthio group in compounds 5a-d and 6a-d was substituted with cyanomethyl group by reaction with lithioacetonitrile to give compounds 11a-d and 10b, c respectively.     

Palladium-Catalyzed Asymmetric [4+3] Cyclization of Trimethylenemethane: Regio-, Diastereo-, and Enantioselective Construction of Benzofuro[3,2-b]azepine Skeletons

The palladium-catalyzed asymmetric [4+3] cyclization of trimethylenemethane donors with benzofuran-derived azadienes furnishes chiral benzofuro[3,2-b]azepine frameworks in high yields (up to 98 %) with exclusive regioselectivities and excellent stereoselectivities (up to >20:1 d.r., >99 % ee). This catalytic asymmetric [4+3] cyclization of Pd-trimethylenemethane can enrich the arsenal of Pd-TMM reactions in organic synthesis. In addition, this strategy provides an alternative approach to chiral azepines by a transition-metal-catalyzed asymmetric [4+3] cyclization.     

Solution and solid-state properties of highly fluorescent dithieno[3,2-b:2',3'-d]pyrrole-based oligothiophenes

Dithieno[3,2-b:2',3'-d]pyrrole-based terthiophene and quaterthiophene analogues have been prepared from N-functionalized dithieno[3,2-b:2',3'-d]pyrroles (DTPs) via Stille coupling. In order to thoroughly study the structure-function property relationships within these DTP-based oligothiophenes, an oligomer series was prepared that allows for the investigation of a number of structural effects including chain length, thiophene functionalization, and pyrrole N-functionalization. As pyrrole N-functionalization allows the incorporation of solubilizing side chains without the unwanted steric interactions that typically reduce backbone planarity, the effect of the bulk of these side chains on the optical properties in both solution and the solid state has been carefully investigated. The DTP-based quaterthiophene, N-tert-butyl-2,6-bis(2'-thienyl)dithieno[3,2-b:2',3'-d]pyrrole was characterized via X-ray crystallography and was found to crystallize in the monoclinic space group P2(1)/c with a = 17.489(4) ?, b = 7.8855(16) ?, c = 14.540(3) ?, β = 108.37(3)°, and Z = 4. The effect of side chains on the solid-state packing of the DTP-based quaterthiophenes was further investigated through X-ray diffraction of solution processed thin films. In comparison to the parent oligothiophenes, the resulting DTP-based systems exhibit enhanced fluorescence efficiencies in solution (up to 66%) and measurable solid-state emission from thin films.     

钯催化三亚甲基甲烷的不对称[3+4]环加成反应:高区域选择性、高非对映选择性和高对映选择性构筑苯并呋喃[3,2-b]吖庚因

环加成反应是构建多官能团化环状化合物最直接、有效的方法之一.其中,三亚甲基甲烷(Trimethylenemethane,TMM)活性中间体被视为一类高效的三碳合成子.目前TMM已被广泛用于多种环加成反应,为一些重要的环状化合物以及天然化合物提供了高效、可靠的合成方法.早在1979年,Trost和Chan等[1]首次报道了Pd-TMM的[3+2]环加成反应.此后,钯催化TMM的多种催化不对称[3+2],[3+3]和[3+6]环加成反应相继得以实现[2,3],并为手性五元环、六元环及九元环类化合物提供了高效的合成策略.然而,对于钯催化TMM的不对称[3+4]环加成化反应——合成七元环状化合物的研究,目前尚无相关报道.其可能的主要原因是七元环状化合物的合成存在不利的熵效应和环化张力.     

Heterocycles [h]-fused onto 4-oxoquinoline-3-carboxylic acid, Part VI [1]. Synthesis and X-ray structure of model indolo[3,2-b]- and [2,3-b]pyrido[2,3-f]quinoxaline-3-carboxylic esters

Cyclocondensation reaction of ethyl 7,8-diamino-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate with 1-methylisatin produced a separable mixture of the corresponding indolo[3,2-b]- and [2,3-b]pyrido[2,3-f]quinoxaline-3-carboxylates, of which the latter isomer predominates. On the other hand, interaction with 1H-isatin or 5-chloroisatin gave the respective indolo[2,3-b]pyrido[2,3-f]quinoxaline-3-carboxylates as the sole regiospecific products. The structures of these new pentacyclic derivatives are based on microanalytical, spectral (IR, MS, and NMR) and X-ray crystal structure data.