Synthesis of Chalcogenophenes via Cyclization of 1,3‐Diynes Promoted by Iron(III) Chloride and Dialkyl Dichalcogenides

In this paper, we report the iron(III) chloride and dibutyl diselenide‐mediated cyclization of 1,3‐diynes which leads to 3,4‐bis(butylselanyl)selenophenes. The optimization studies showed that the reaction was best performed with equimolar amounts of iron(III) chloride and dibutyl diselenide in dichloromethane at 40 °C for 4 h. The method allows the synthesis of symmetrical and unsymmetrical selenophenes in moderate to good yields. A similar protocol was also extended to the synthesis of thiophene derivatives using dimethyl disulfide instead of dibutyl diselenide. The resulting selenophenes and thiophenes were further functionalized by selenium–halogen exchange reactions, Sonogashira cross‐coupling reactions and electrophilic cyclizations.

     

On Dimensionality of Halogen-Bonded Thiophene Solid-State Assemblies

We report on the structures of three dibromothiophene compounds ( 4 , 5 , and 12 ) and the analysis of the patterns of self-assembly in the solid state by C Br⋅⋅⋅Br C halogen bonds of a selected set of 16 di- or poly-bromine (poly)thiophene monomers sorted according to the dimensionality of their halogen-bonded, extended frameworks thereby identifying syn- or anti-strings and layers. We conclude that in 1 , 2 , 9 , and 10 , the antiparallel orientation of successive C Br⋅⋅⋅Br C halogen-bonded dibromothiophene units along extended anti-strings is linked to the occurrence of solid-state polymerization.     

以芳香胺为反应底物相转移催化下合成联芳化合物

提出了在三氯乙酸、铜粉、季铵盐相转移催化剂TBAB存在下,以亚硝酸戊酯为重氮化试剂,芳香胺与其它芳香化合物偶联一步生成联芳化合物的方法。研究表明,使用季铵盐相转移催化剂可使反应产率提高10%~20%,最佳反应温度为30~40℃。并用此方法合成了3个系列21个化合物。     

Highly Regioselective DABCO‐Catalyzed Nucleophilic Aromatic Substitution (SNAr) Reaction of Methyl 2,6‐Dichloronicotinate with Phenols

Exclusive formation of 6‐aryloxy ethers 9 from an S_NAr reaction of methyl 2,6‐dichloronicotinate ( 2 ) with phenols 7 catalyzed by 1,4‐diazabicyclo[2.2.2]octane (DABCO) in the presence of stoichiometric triethylamine is described. The reaction proceeds via the regioselective formation of an unprecedented DABCO‐pyridine adduct 10a .     

2,3‐Disubstituted Benzo[b]thiophenes from Diarylalkynes via Electrophilic Addition‐Cyclization and Palladium‐Catalyzed Cross‐Coupling

Diarylalkynes are readily transformed in 3‐chlorobenzo[b]thiophenes in a two‐step electrophilic addition‐cyclization procedure that runs highly efficiently in solution or in the solid phase. The heteroaromatic carbon‐chlorine bond participates in palladium‐catalyzed Suzuki–Miyaura or Buchwald–Hartwig cross‐couplings to give, in a single step, 2,3‐disubstituted derivatives of pharmacological relevance .     

Direct Arylation of Thiophenes via Palladium‐Catalysed C?H Functionalisation at Low Catalyst Loadings

Palladium associated with cis,cis,cis‐1,2,3,4‐tetrakis(diphenylphosphinomethyl)cyclopentane (Tedicyp) was found to promote the direct 2‐arylation of a variety of thiophene derivatives via C H functionalisation in good yields using very low catalyst loadings. Electron‐deficient, electron‐excessive or sterically‐congested aryl bromides are tolerated. Moreover, several substituents on the aryl bromide or thiophene derivatives such as acetyl, formyl, nitrile, nitro, ester, methoxy, fluoro or trifluoromethyl are tolerated. The most reactive aryl bromides were coupled with thiophenes derivatives using as little as 0.1–0.01 mol % catalyst.     

Iron‐Promoted Tandem Cyclization of 1,3‐Diynyl Chalcogen Derivatives with Diorganyl Dichalcogenides for the Synthesis of Benzo[b]furan‐Fused Selenophenes

A double intramolecular 5‐endo‐dig cyclization of butyl[2‐(phenylbuta‐1,3‐diynyl)phenyl]chalcogens has been employed in a selective preparation of benzo[b]chalcogenopheno[2,3‐d]furans. Several reaction parameters were studied to determine the best reaction conditions and we observed that the reaction of butyl[2‐(phenylbuta‐1,3‐diynyl)phenyl]chalcogens (0.25 mmol) with iron(III) chloride hexahydrate (2.0 equiv.) and diorganyl diselenides (1.75 equiv.) at reflux of dichloromethane was the most appropriate to give the products in 35–89% yields. These standard reaction conditions were compatible with many functional groups in the substrates, such as methyl, chlorine, fluorine, methoxy and heteroaryl. This protocol was also efficient for diorganyl diselenides but it was ineffective with diorganyl disulfides and ditellurides. In a competition among selenium, sulfur and oxygen nucleophiles we observed that the nucleophilicity and steric effects of the competing functional groups were determinant factors for the selectivity of the cyclization. The benzo[b]chalcogenopheno[2,3‐d]furans had absorptions in the UV region (300–350 nm range) with molar absorptivity coefficient values ascribed to spin and symmetry allowed π–π* electronic transitions. An emission located in the purple region (380–440 nm range), with a Stokes shift of between 65–100 nm, is probably associated to the charge transfer character of the excited state.

     

Organic-skinned inorganic nanoparticles: surface-confined polymerization of 6-(3-thienyl)hexanoic acid bound to nanocrystalline TiO2

There are many practical difficulties in direct adsorption of polymers onto nanocrystalline inorganic oxide surface such as Al2O3 and TiO2 mainly due to the insolubility of polymers in solvents or polymer agglomeration during adsorption process. As an alternative approach to the direct polymer adsorption, we propose surface-bound polymerization of pre-adsorbed monomers. 6-(3-Thienyl)hexanoic acid (THA) was used as a monomer for poly[3-(5-carboxypentyl)thiophene-2,5-diyl] (PTHA). PTHA-coated nanocrystalline TiO2/FTO glass electrodes were prepared by immersing THA-adsorbed electrodes in FeCl3 oxidant solution. Characterization by ultraviolet/visible/infrared spectroscopy and thermal analysis showed that the monolayer of regiorandom-structured PTHA was successfully formed from intermolecular bonding between neighbored THA surface-bound to TiO2. The anchoring functional groups (-COOH) of the surface-crawling PTHA were completely utilized for strong bonding to the surface of TiO2.     

Toward High Thermoelectric Performance of Thiophene and Ethylenedioxythiophene (EDOT) Molecular Wires

The design of thermoelectric materials for the efficient conversion of waste heat into electricity requires simultaneous tuning of their electrical and thermal conductance. A comparative theoretical study of electron and phonon transport in thiophene and ethylenedioxythiophene (EDOT) based molecular wires is performed. It is shown that modifying thiophene by substituting ethylenedioxy enhances the thermoelectric figure of merit ZT for molecules of the same length. Furthermore, it is demonstrated that the electrical conductance of EDOT‐based wires decays more slowly with length than that of thiophene‐based wires and that their thermal conductance is lower. The room‐temperature ZT of undoped EDOT is found to be rather low. However, doping of EDOT by the electron acceptor tolunenesulfunate increases the Seebeck coefficient and electrical conductance, while decreasing the thermal conductance, leading to a thermoelectric figure of merit as high as ZT = 2.4.     

Synthesis of anti-microtubule biaryls and preliminary evaluation as vascular-disrupting agents

A series of new dibenzoxepines were synthesized in a straightforward and efficient manner through diastereoselective biaryl Suzuki–Miyaura coupling and Brønsted‐acid‐mediated cyclodehydration as key steps. The vascular‐disrupting potential of these molecules was evaluated with various in vitro assays: inhibition of microtubule assembly, antiproliferative activity against cancer cell lines and normal endothelial cells, modification of endothelial cell morphology, and disruption of endothelial cell cords. Two of these compounds showed promising activities in these assays, with profiles similar to that of the reference drug NAC and markedly different from that of colchicine. Altogether, these results show that dibenzoxepines represent promising new leads for the development of more selective vascular‐disrupting agents.