Syntheses and Properties of Donor−Acceptor-Type 2,5-Diarylthiophene and 2,5-Diarylthiazole

Selective mono- to perarylations of tetrabromothiophene by a cyclobutene-1,2-diylbisimidazolium preligand

(Cyclobut-1-ene-1,2-diyl)bis(1-methylimidazolium)tetrafluoroborate is applied as preligand in palladium-catalyzed cross-coupling reactions starting from tetrabromothiophene for the synthesis of mono-, bi-, tri-, and tetraaryl-substituted thiophenes bearing up to four different aryl rings. A synthetic kit for preparations of nine different substitution patterns of arylated thiophenes is presented by application of only one single catalyst system. In agreement with DFT calculations, which predict energetically low rotational barriers in triaryl-3-bromothiophenes and tetraarylthiophenes, no NOE effects between adjacent aryl rings are detectable. The regioselectivity of their syntheses has therefore been elucidated by reduction of triaryl-3-bromothiophene to 2,3,5-triarylthiophene followed by HMBC, HSQC, and NOESY NMR measurements. Additionally, results of an X-ray single structure analysis are presented.

1-{5-[2-Chloro-5-(trifluoromethyl)phenyl]thiophen-2-yl}ethanone

In the title molecule, C₁₃H₈ClF₃OS, the dihedral angle between the mean planes of 2-chloro-5-(trifluoro­meth­yl)phenyl and tiophene rings is 54.37 (5)°. The acethyl group is twisted by 8.1 (2)° with respect to the thio­phene ring. The CF₃ group is disordered over two sets of sites with occupations of 0.49 (3) and 0.51 (3). The crystal packing features C—H⋯F and C—H⋯O hydrogen bonds, forming dimers which are connected into chains along the c axis by C—H⋯O hydrogen bonds and C—Cl⋯π [Cl⋯π = 3.415 (1) Å and C—Cl⋯π = 151.56 (5)°] inter­actions. The chains are further connected into layers perpendicular to the a axis by C—H⋯O inter­actions.

Silver-mediated palladium-catalyzed direct C-H arylation of 3-bromoisothiazole-4-carbonitrile

Silver(I) fluoride-mediated Pd-catalyzed C-H direct arylation/heteroarylation of 3-bromoisothiazole-4-carbonitrile (1a) gives twenty-four 5-aryl/heteroaryl-3-bromoisothiazole-4-carbonitriles. The reaction was partially optimized with respect to catalyst, ligand, and base. During this study 3,3'-dibromo-5,5'-biisothiazole-4,4'-dicarbonitrile (3a) was isolated as a byproduct and subsequently prepared via the silver-mediated Pd-catalyzed oxidative dimerization of 3-bromoisothiazole-4-carbonitrile in 67% yield. The analogous phenylation and oxidative dimerization of 3-chloroisothiazole-4-carbonitrile (1b) gave 3-chloro-5-phenylisothiazole-4-carbonitrile (4) and 3,3'-dichloro-5,5'-biisothiazole-4,4'-dicarbonitrile (3b) in 96% and 69% yields, respectively.

Synthesis and evaluation of new arylbenzo[b]thiophene and diarylthiophene derivatives as inhibitors of the NorA multidrug transporter of Staphylococcus aureus

The synthesis based on palladium catalytic coupling of 38 new-arylated benzo[b]thiophenes or thiophenes is described in a few steps. We also report the direct arylation of the position 3 of the benzo[b]thiophenic structure, a 'one pot' 2,5-heterodiarylation of thiophenes as well as the synthesis of precursors of amino-acids with a 2-arylated benzo[b]thiophene core. These compounds were evaluated on bacteria strains: most of them did not exhibit any antibiotic activity but were found to selectively inhibit the NorA multidrug transporter of Staphylococcus aureus. As such, they restored the activity of the NorA substrates ciprofloxacin against a resistant S. aureus strain in which this efflux pump is over-expressed.

Optical behaviors of conjugated-chain compounds containing benzene and furan units

Thirteen conjugated-chain compounds which contain benzene and furan units were prepared, their optical behaviors, including UV-vis absorption coefficient (epsilon), absorption wavelengths (lambdaa), fluorescence emission wavelengths (lambdae), and quantum yields (Phi) were measured. Meanwhile, their LUMO and HOMO energy were determined by cyclic voltammetry and their second-order polarizations (betaxxx) values were determined by solvatochromic method, respectively. The results showed that this kind of compounds possess a shorter lambdaa (320-365 nm) and performance a higher Phi values, especially for 2aa, 2ab, 2ac and 2bb, their Phi values are all more than 90%. These compounds, except 2db, showed a higher betaxxx values in DMSO, especially for 2dc (75.77x10(-30) m5 C-1) and 2dd (83.32x10(-30) m5 C-1), than that 10-methyl-acridone (6.578x10(-30) m5 C-1) or 10-benzylacridone (6.845x10(-30) m5 C-1) in DMSO did, and second harmonic generation value of 10-methylacridone and 10-benzylacridone in powder are, respectively, 1.381 and 1.861 times of that value of urea. The betaxxx values and Phi values determined for these compounds in this work were lower than these values which were desired in the original work, this phenomena was explained from their molecular structures. This work confirmed that as these compounds performance shorter lambdaa and higher Phi values, they could be good blue-color optical materials for some fields, such as OLED materials, two-photo absorption materials, fluorescent dyes.

Photoluminescent and Liquid-Crystalline Properties of Donor–Acceptor-Type 2,5-Diarylthiazoles

The synthesis of donor-acceptor-type 2,5-diarylthiazoles that bear electron-donating N,N-dialkylamine and electron-withdrawing cyano groups at the 2- and 5-position, respectively, were carried out with transition-metal-catalyzed C-H arylation reactions developed by us. The compounds were synthesized by the C-H arylation of unsubstituted thiazole at the 2-position with a palladium/copper catalyst in the presence of tetrabutylammonium fluoride (TBAF) as an activator. Further C-H arylation of the 2-arylated thiazole at the 5-position was carried out by the palladium-catalyzed reaction in the presence of silver(I) fluoride to afford the donor-acceptor-type 2,5-diarylthiazoles with N,N-dialkylamine groups of different chain lengths. The UV/Vis absorption, photoluminescence, and electrochemical behavior were similar regardless of chain length, whereas liquid-crystalline behavior and thermal characteristics were found to be dependent on the alkyl-chain length. The compounds with N,N-diethylamine or N-butyl-N-methyl groups showed a stable liquid-crystalline phase over a wide temperature range as well as higher stability to thermal decomposition.