Investigations of substituted benzofuran-3-carboxylates,benzo[1,2-b:4,5-b']difurans and benzo[1,2-b:4,3-b']difurans

The Michael addition of ethyl acetoacetate to benzoquinone, toluquinone, and chlorobenzo-quinone leads to formation of substituted 5-hydroxybenzofuran-3-earboxylates and linear benzo-[1,2-b:4,5-b']difurans. The previously reported structural proof for the benzodifurans obtained from chlorobenzoquinone and toluquinone, although correct in the conclusion, is shown to be invalid. Proof of the linear benzodifuran structures was obtained by comparison of the uv spectra with authentic angular benzo[1,2-b:4,3-b']difurans.     

Facile synthesis, structure, and properties of benzo[1,2-b:4,5-b']dichalcogenophenes

[reaction, structures: see text] A general and convenient synthesis of benzo[1,2-b:4,5-b']dichalcogenophenes including the thiophene (BDT, 1), selenophene (BDS, 2), and tellurophene (BDTe, 3) homologues is developed. Thus synthesized heterocycles are structurally characterized by single-crystal X-ray analysis, and all three homologues are isostructural with one another. They all have completely planar molecular structures packed in a herringbone arrangement. Their physicochemical properties were also elucidated by means of cyclic voltammetry (CV) and UV-vis spectra.     

Benzo[1,2-b:4,5-b']bis[b]benzothiophene as solution processible organic semiconductor for field-effect transistors

Coplanar benzo[1,2-b:4,5-b']bis[b]benzothiophenes (, ) for the application in organic field-effect transistors were synthesized by a simple two-step procedure involving triflic acid induced ring-closure reaction; such solution processed devices show a hole mobility of up to 0.01 cm(2) V(-1) s(-1).     

The preparation of the benzo[4,5]cyclohepta[1,2-b]pyrazine and benzo[4,5]cyclohepta[1,2-b]quinoxaline systems

Benzo[4,5]cyclohepta[1,2-b]quinoxaIine 2 , benzo[4,5]cyclohepta[1,2-b]pyrazine 3a and benzo[4,5]cyclohepta[1,2-b]quinoxaline 4 were prepared from 4,5-benzotropolone and 1,2-phenylenediamine, ethylenediamine and 1,2-diaminocyclohexane, respectively. Compound 3a was methylated to 3b .     

2,3,9,10-Tetrachlorobenzo[1,2-b: 4,5-b']bis[1,4]benzodioxin,a homologue of TCDD

Catechol and 4,5-dichlorocatechol have been condensed with 1,5-dichloro-2,4-dinitrobenzene to provide benzo[1,2-b: 4,5-b ]bis[1,4]benzodioxin and its 2,3,9,10-tetrachloro derivative, respectively. The latter compound is a novel homologue of the extremely toxic 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD).     

Organic dyes incorporating the benzo[1,2-b:4,5-b']dithiophene moiety for efficient dye-sensitized solar cells

A new class of organic sensitizers incorporating a benzo[1,2-b:4,5-b']dithiophene (BDT) unit as conjugated spacer has been synthesized and successfully used for dye-sensitized solar cells (DSSCs). The length of the π-conjugated spacers has a strong impact on electro-optical properties of these dyes, leading to the conversion efficiencies ranging from 4.17 to 5.68% under AM 1.5 G irradiation. This result indicates that the BDT unit is a promising candidate in organic sensitizers.     

A low band-gap polymer based on unsubstituted benzo[1,2-b:4,5-b']dithiophene for high performance organic photovoltaics

A low band-gap conjugated polymer, PBDTDPP, composed of unsubstituted benzo[1,2-b:4,5-b']dithiophene and diketopyrrolo[3,4-c]pyrrole was synthesized. The deep HOMO level of PBDTDPP enhances the V(OC) of a PSC up to 0.82 V and exhibits a PCE of 5.16%, while alkoxy substituted PBDTDPP-OR yields a PCE of 2.24% with a V(OC) of 0.61 V.     

A novel dialkylthio benzo[1,2-b:4,5-b']dithiophene derivative for high open-circuit voltage in polymer solar cells

A new dialkylthio benzo[1,2-b:4,5-b']dithiophene (S-BDT) was designed and synthesized and the polymer S-PBDT was prepared by a Stille coupling reaction. A high open-circuit voltage (V(oc)) of up to 0.99 V was achieved in polymer solar cells with PCBM.     

A new route to benzo[4,5]cyclohepta[1,2-b]naphthalenes: synthesis of radermachol

[formula: see text] Condensation of 3-phenylsulfonyl-1,3-isobenzofuranone (3) with benzocyclohept-6,7-en-5-ones such as 4 and 15 provides a straightforward, general method for synthesis of functionalized benzo[4,5]cyclohepta[1,2-b]naphthalenes (e.g., 5 and 16). This finding was used to achieve a brief and efficient preparation of 6,7-benzo-3,4-(1,4-dimethoxy-2,3-naphtho)-1,5-dioxosuberane (2), an established intermediate to the naturally occurring red pigment radermachol (1).     

New reaction of benzo[b]thieno[3,2-b]benzo[b]thiophene disulfone

A new reaction of benzo[b]thieno[3,2-b]benzo[b]thiophene disulfone with amines that takes place with opening of one of the thiophene rings and nucleophilic substitution in the heteroaromatic ring at the site of cleavage of the S-C bond was observed. The molecular structures of the products of amination of the disulfone were determined by x-ray diffraction analysis. Hydrolysis and dehydration of the amination products gave derivatives of a new heterocyclic system, viz., benzo[b]-thieno[3,2-e]benzo[c]-1,2-oxathiin. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 320–323, March, 1980.     

Synthesis and characterization of benzo[1,2-b:3,4-b':5,6-b']trithiophene (BTT) oligomers

Two dimers (2 and 3), dendritic tetramer (4), hexamer (5), and decamer (6) of benzo[1,2-b:3,4-b':5,6-b']trithiophene (BTT), a potential π-core unit with C(3h) symmetry, were synthesized, characterized, and evaluated for possible use as organic semiconductors. Single crystal X-ray analyses of the dimers (2 and 3) revealed that they have planar molecular structures with dihedral angles of almost 180° between two BTT units. In accordance with the rigid and planar molecular structure, the unsubstituted dimer (2) is poorly soluble, whereas the octyl-substituted dimer (3) has improved solubility. Although the solubility of the dendritic tetramer (4) is decreased, further extended systems, i.e., the dendritic hexamer (5) and decamer (6), have solubilities better than that of 4. With increasing numbers of BTT units in the molecule, the experimentally determined energy levels of HOMO shift upward slightly and the HOMO-LUMO energy gaps become smaller, but the extent of HOMO destabilization and reduction of the HOMO-LUMO gap are not significant. Taking into account the energy levels of the frontier orbitals, 3-6 could be useful as p-channel organic semiconductors rather than n-channel. In fact, the spin-coated thin film of 3 with edge-on molecular orientation acted as an active channel of field-effect transistors that showed hole mobilities as high as 0.14 cm(2) V(-1) s(-1), indicating that the BTT core is a useful π-conjugated system for application to organic semiconductors, although 4-6 gave FET characteristics rather inferior to those of 3, owing to their amorphous nature in the thin film state.     

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes: a new class of high-performance semiconductors for organic field-effect transistors

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes including thiophene, selenophene, and tellurophene analogues as organic semiconductors for field-effect transistors were effectively synthesized in three steps from commercially available 1,4-dibromobenzene. All three benzodichalcogenophenes acted as good p-type semiconductors, and particularly the selenophene analogue, 2,6-diphenylbenzo[1,2-b:4,5-b']diselenophene, showed high FET mobility of 0.17 cm2 V-1 s-1.     

Synthesis, electronic properties, and X-ray structural characterization of tetrarylbenzo[1,2-b:4,5-b']difuran cation radicals

Electroactive tetraarylbenzo[1,2- b:4,5- b']difuran (BDF) and model diarylbenzofuran derivatives are synthesized and their structures are established by X-ray crystallography. Isolation and X-ray crystallographic characterization of the robust cation-radical salts of BDF derivatives confirm that a single charge in the BDFs is stabilized largely by the benzodifuran and coplanar alpha-aryl groups lying on the longitudinal axis. These findings suggest that the linear arrays of BDFs may allow the construction of molecular wires suitable for long-range electron transport.     

Convenient synthesis of 5,6,11,12,17,18- hexahydrocyclononal[1,2-b:4,5-b':7,8-b'']triindole,a novel phytoestrogen

An efficient one-pot synthesis is described of 5,6,11,12,17,18-hexahydrocyclononal[1,2-b:4,5-b':7,8-b']triindole (CTr), a potent estrogen agonist from food plants. For the procedure, gramine is treated with dimethyl sulfate and sodium in ethanol at room temperature. Quenching of the reaction with water and workup of the product provides CTr in approximately 75% yield.     

Nucleophilic addition to benzo[b]thieno[2,3-b]benzo[b]thiophene S,S,S′,S′-tetroxide

The reaction of benzo[b]thieno[2,3-b]benzo[b]thiophene S,S,S′,S′-tetroxide with primary and secondary amines and with alcohols gave 10 b-amino- and 10 b-alkoxy-5a, 10b-dihydro-benzo[b]thieno[2,3-b]benzo[b]thiophene S,S,S′,S′-tetroxides. These nucleophilic reagents do not add to benzo[b]thieno[2,3-b]benzo[b]thiophene S,S-dioxide.     

Synthesis of a 4,8-dialkoxy-benzo[1,2-b:4,5-b']difuran unit and its application in photovoltaic polymer

A new building block of benzo[1,2-b:4,5-b']difuran (BDF) was firstly designed and synthesized. The newly designed unit was applied for constructing a new photovoltaic low band gap polymer, PBDFDTBT, which exhibited promising power conversion efficiency of 5.0%.     

Derivatives of benzo[4,5]cyclohepta[1,2-b]thiophene. 4. Synthesis of 1-(9,10-dihydro-4H-benzo[4,5]cyclohepta[1,2-b]thiophen-4-yl)-3-alkylaminoazetidines

Thirteen 1-(9,10-dihydro-4H-benzo[4,5]cyclohepta[1,2-b]thiophen-4-yl)-3-alkylaminoazetidines 11 have been synthesized in three steps from 4-amino-9,10-dihydro-4H-benzo[4,5]cyclohepta[1,2-b]thiophene ( 6 ), which was obtained from the reduction of either 4-azido 4 or 4-hydroxyimino 5 derivatives. All the compounds have been evaluated as potential antidepressive agents.     

A Near-infrared Non-fullerene Acceptor with Thienopyrrole-expanded Benzo[1,2-b:4,5-b′]dithiophene Core for Polymer Solar Cells

A near-infrared non-fullerene acceptor(NFA) BDTIC, based on thienopyrrole-expanded benzo[1,2-b:4,5-b′]dithiophene unit(heptacyclic S,N-heteroacene) as core, is designed and synthesized. The aromatic pyrrole ring with strong electron-donating ability in the core enhances the intramolecular charge transfer effect, finely tunes the optical bandgap and absorption profile of BDTIC, and thus results in a narrowed optical bandgap(E_g~(opt)) of 1.38 eV and a near-infrared absorption to 900 nm. When BDTIC is paired with donor polymer PBDB-T to fabricate organic solar cells, the optimized device achieves a best power conversion efficiency of 12.1% with a short-circuit current density of 20.0 mA·cm~(-2) and an open-circuit voltage of 0.88 V. The photovoltaic performance benefits from the broad absorption, weak bimolecular recombination, efficient charge separation and collection, and favorable blend morphology. This work demonstrates that thienopyrroleexpanded benzo[1,2-b:4,5-b′]dithiophene unit(heptacyclic S,N-heteroacene) is a promising building unit to construct high-performance NFAs by enhancing the intramolecular charge transfer effect, broadening absorption as well as maintaining good intermolecular stacking property.     

Synthesis of 1H-[1,2]diazepino[4,5-b]indole derivatives

A synthesis of four 1H-[1,2]diazepino[4,5-b]indole derivatives and some preliminary information about their biological activity are presented. The starting materials were 2-ethoxycarbonylindoles and 2-ethoxy-carbonyl-3-formylindoles, la, b and 2a, b, respectively. 2-Ethoxycarbonyls la, b reacted with 1-dimethylamino-2-nitroethylene and -2-ethoxycarbonyl-3-formylindoles 2a, b in the presence of nitroalkanes (nitromethane or nitroethane) giving 3-(2-nitrovinyl)indoles 3a, b. Reduction of 3a, b yielded β-(2-oxoalkyl)indoles 4. On reaction with an excess of hydrazine hydrate, compounds 4 gave satisfactory yields of 5-oxo-1H-[1,2]diazepino[4,5-b]indoles 5.     

Synthesis and properties of a series of well-defined and polydisperse benzo[1,2-b:4,3-b']dithiophene oligomers

Monodisperse and polydisperse oligomers of benzo[1,2-b:4,3-b']dithiophene (BDT) (1-14), including three types of oligomers with different spacers combining BDT units (direct linkage, vinylene spacers, and ethynylene spacers), were synthesized, and their thermal, optical, and electrochemical properties were investigated. The oligomers were synthesized using Suzuki, Stille, Wittig, and Sonogashira coupling reactions. All of the monodisperse oligomers showed high melting points and 5% weight loss temperatures (T(d) > 400 degrees C). The fluorescence maxima of all oligomers were red-shifted, and the emission colors varied from blue to yellow as the chain lengths-and thus the conjugation lengths-increased. The vinylene-bridged oligomers emitted at longer wavelengths than the direct-linked and ethynylene-bridged oligomers. UV-vis absorption spectra in toluene solution indicated an effective conjugation length of about six BDT units for polydisperse oligomer 5. Cyclic voltammetry measurement indicated that tetramer 3 had high electrochemical stability. Although tetramer 3 and vinylene-bridged tetramer 8 exhibited reversible oxidation waves, ethynylene-bridged tetramer 13 showed an irreversible oxidation process. Each type of monodisperse oligomer exhibited higher HOMO levels with increasing chain length.