Mild and highly regioselective synthesis of biaryl acids via Rh (I)-catalyzed cross-dehydrogenative coupling of benzoic acids using sodium chlorite as oxidant

A mild and efficient synthesis for the biaryl acids via rhodium-catalyzed cross-dehydrogenative coupling reaction has been developed. This novel protocol with sodium chlorite as an oxidant featured many advantages such as mild reaction conditions, high regioselectivity, tolerance of various functional groups, and good to excellent yields.

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The synthesis,characterization, and structure of a series of 4H-thieno[3,4-c]pyrroles and their corresponding pyrrolium cyanoborohydride salts

A general, convenient route toward N-substituted 5,6-dihydro-4H-thieno[3,4-c]pyrroles was accomplished by the reductive amination of 2,5-dimethylthiophene-3,4-dicarbaldehyde with various primary amines in a solution of sodium cyanoborohydride and methanol/acetic acid (80–88% yield). For the N-alkyl cases, the product isolated was the cyanoborohydride salt of the desired product, 1,3-dimethyl-5-alkyl-5,6-dihydro-4H-thieno[3,4-c]-5-pyrrolium cyanoborohydride. For the aryl case employing aniline, the desired free pyrrole, 1,3-dimethyl-5-phenyl-5,6-dihydro-4H-thieno[3,4-c]pyrrole, was isolated. X-ray crystallographic analysis of both the N-propyl and N-phenyl trials confirmed the salt and free amine nature of the products.     

Water as Solvent for Nickel‐2,2′‐Bipyridine‐Catalysed Electrosynthesis of Biaryls from Haloaryls

Reductive homocoupling of aryl halides into biaryls was achieved by electrolysis of aqueous emulsions, either in an undivided cell fitted with a sacrificial anode, or in a divided diaphragm cell, and in the presence of nickel‐2,2′‐bipyridine as catalyst. Reactions were also run in a filter‐press cell.     

One‐Pot Synthesis of Biaryl Lactones by Sonogashira Cross‐Coupling Reactions of 4‐Chloro‐3‐formylcoumarin and Subsequent Domino [5+1] Cyclization/Deacetylation Reactions with 1,3‐Dicarbonyl Compounds

Biaryl lactones were prepared by a new palladium(0) and base‐catalyzed one‐pot reaction of 4‐chloro‐3‐formylcoumarin with alkynes and 1,3‐dicarbonyl compounds.     

Novel aminophosphonothiophene derivatives from β-keto-δ-carbethoxyphosphonates and phosphineoxides

The reaction of β-keto-δ-carbethoxyphosphonates and phosphineoxides with active methylene nitriles leads to the corresponding phosphonoalkylidenes. Treatment of these compounds with sulfur, under the classical Gewald reaction conditions, gives a ca. 1:1 mixture of novel aminophosphonothiophene derivatives 3 and 3 ^′ . In order to improve the regioselectivity of the reaction, novel conditions have been developed for the Gewald condensation, in which we used an inorganic base NaH in THF as the solvent. These conditions afforded exclusively the 3-regioisomer in good yield.

     

Solvent and Temperature Effects on Spectral Properties of Two Poly （3-alkyl） thiophene Derivatives

Two alkyl substituted polythiophene derivatives : poly (3-hexylthiophene) ( P3 HT) and poly ( 3- decyhhiophene) (P3DT), have synthesized by oxidation coupling polymerization of 3-alkylthiophene using iron (Ⅲ) chloride as catalyst in chloroform. While both polymers in pure chloroform solution have maximum absorption at approximately same wavelength of 440 nm, they behave differently with respect to changes observed on their UV-visible and photoluminescence spectra when the quality of the poor solvent is changed in good solvent (chloroform) / poor solvent (methanol) mixtures. With increasing volume fraction of methanol in mixtures, the absorption spectra of P3HT and P3DT red-shift, peaking at maximum wavelength of 495 nm (P3HT) and 510 nm(P3DT). Furthermore, the absorption spectra of the two polymers in chloroform blueshift as the temperature rises. P3HT shows 4.73 nm blue-shifts at 50 ℃ in contrast to the case at 20 ℃, while P3DT blue-shifts about 5.04 nm. The photoluminescence spectra of the two polymers in mixed solution are also investigated, which show that the luminescence spectra shift to longer wavelength with an accompanying drop in the PL intensity as methanol is increased. The absorption and emission spectra of the two polymers in a poor solvent and a thin film are similar, which indicate that a similar longer conjugation length in the two cases. It could conclude that the polymers exist almost the same conformations and aggregations in both a poor solvent and a thin film. P3DT exhibits more sensitive spectra properties (big red-shifts in both absorption and luminescence spectra in poor solvents and large blue-shifts at high temperature) with contrast to P3HT, which imply that long side alkyl may improve the chromic properties of the polymer.     

Complex Extraction of Thiophenes Using Room Temperature Ionic Liquids

Two kinds of room temperature ionic liquids (RTILs) 1-butyl-3-methyl limidazolium chloroaluminate (III) ([bmim]Cl+AlCl₃) and 1-butyl-3-methyl limidazolium hexfluorophosphate ([bmim]PF6) were synthesized, respectively, and the removal of thiophenes from refined diesel was studied by the method of complex extraction. The results showed that under the best operational conditions, the content of thiophenes went down 46 wt% in chloroaluminate RTIL and 69 wt% in hexfluorophosphate RTIL, and other properties of diesel were improved at the same time. Both of the two kinds of RTILs can be used for several times through regenerating.     

Light-mediated allelochemical effects of naturally occurring polyacetylenes and thiophenes from asteraceae on herbivorous insects

Polyacetylenes and their thiophene derivatives, characteristic secondary metabolites of the Asteraceae, were examined for their effects on herbivorous insects. Three thiophenes (a monothiophene, a bithiophene, and -terthienyl) and four polyacetylenes (phenylheptatriyne, phenylheptadiynene, phenylheptadiyene acetate, and matricaria lactone) were studied for their phototoxicity and light-independent toxicity to (1) a polyphagous lepidopteran,Ostrinia nubilalis, whose host range includes a number of phototoxic Asteraceae, (2) a polyphagous lepidoteran,Euxoa messoria, whose host range includes very few species of Asteraceae, and (3) an oligophagous lepidopteran,Manduca sexta, which is a specialist on Solanaceae. Several compounds were phototoxic toM. sexta andE. messoria even at very low irradiance levels, but behavioral adaptations, including spinning silk and boring into diet, allowedO. nubilalis to avoid photosensitization. Light-independent activity of the compounds to all three species involved feeding deterrence increasing in the orderO. nubilalis, E. messoria, andM. sexta, and longterm metabolic toxicity in the form of impaired nutrient utilization. The biosynthetically derived thiophenes were more toxic than their acetylenic precursors, and toxicity increased with increasing number of thiophene rings. The results are discussed in terms of plant-insect coevolution.     

Regioselective Palladium(0)‐Catalyzed Cross‐Coupling Reactions and Metal‐Halide Exchange Reactions of Tetrabromothiophene: Optimization,Scope and Limitations

The Suzuki reaction of tetrabromothiophene with arylboronic acids provides a regioselective approach to various 5‐aryl‐2,3,4‐tribromothiophenes, symmetrical 2,5‐diaryl‐3,4‐dibromothiophenes, and tetraarylthiophenes. Unsymmetrical 2,5‐diaryl‐3,4‐dibromothiophenes are prepared by Suzuki reaction of 5‐aryl‐2,3,4‐tribromothiophenes. Tetraarylthiophenes containing two different types of aryl groups are obtained by Suzuki reactions of 2,5‐diaryl‐3,4‐dibromothiophenes. During the optimization of the conditions of each individual reaction, the solvent, the catalyst and the temperature play an important role. In several cases, classical conditions [use of tetrakis(triphenylphosphane)palladium(0), Pd(PPh₃)₄, as the catalyst] gave excellent yields. The yields of those transformations which failed or proceeded sluggishly could be significantly improved by application of a new biarylmonophosphine ligand developed by Buchwald and co‐workers. Regioselective metal‐halide exchange reactions of tetrabromothiophene provide a convenient approach to various 2,5‐disubstituted 3,4‐dibromothiophenes. 5‐Alkyl‐2‐trimethylsilyl‐3,4‐dibromothiophenes could be prepared in one pot by sequential addition of trimethylchlorosilane and alkyl bromides. The reaction of tetrabromothiophene with methyl chloroformate and subsequent Suzuki reactions afforded 3,4‐diaryl‐2,5‐bis(methoxycarbonyl)thiophenes.