Li-Rong Wen

Extended isoindigo core: synthesis and applications as solution-processable n-OFET materials in ambient conditions

Two isoindigo derivatives fused with benzothiophene (C20-DBTII) and benzofuran (C20-DBFII) heterocycles have been synthesized. Solution-processed OFETs based on C20-DBTII showed ambient-stable ambipolar charge transport behaviour. OFETs based on the C20-DBFII show n-channel behaviour with electron mobility up to 0.074 cm2 V−1 s−1 in ambient conditions.

Reductive ring closure methodology toward heteroacenes bearing a dihydropyrrolo[3,2-b]pyrrole core: scope and limitation.

A newly developed reductive ring closure methodology to heteroacenes bearing a dihydropyrrolo[3,2-b]pyrrole core was systematically studied for its scope and limitation. The methodology involves (i) the cyclization of an o-aminobenzoic acid ester derivative to give an eight-membered cyclic dilactam, and (ii) the conversion of the dilactams into the corresponding diimidoyl chloride, which undergoes (iii) reductive ring closure to install the dihydropyrrolo[3,2-b]pyrrole core. The first step of the methodology plays the key role due to its substrate limitation, which suffers from the competition of oligomerization and hydrolysis. All the dilactams could successfully convert to the corresponding diimidoyl chlorides, most of which succeeded to give the dihydropyrrolo[3,2-b]pyrrole core. The influence of the substituents and the elongation of conjugated length on the photophysical properties of the obtained heteroacenes were then investigated systematically using UV-vis spectroscopy and cyclic voltammetry. It was found that chlorination and fluorination had quite a different effect on the photophysical properties of the heteroacene, and the ring fusing pattern also had a drastic influence on the band gap of the heteroacene. The successful preparation of a series of heteroacenes bearing a dihydropyrrolo[3,2-b]pyrrole core would provide a wide variety of candidates for further fabrication of organic field-effect transistor devices.

A new approach to pyridines through the reactions of methyl ketones with 1,2,4-triazines

A new route to prepare pyridine derivatives based on inverse electron demand Diels–Alder/retro-Diels–Alder reactions of ketones with 1,2,4-triazines is reported. It is the first time using methyl ketones directly as a dienophile to react with 1,2,4-triazines without enamine intermediates, which is complementary to the classical Boger reaction.

Copper-catalyzed tandem arylation–cyclization of 2-alkynylaryl isothiocyanates with diaryliodonium salts: an efficient synthesis of thiochromeno[2,3-b]indoles

A catalytic tandem arylation–cyclization approach using 2-alkynylphenyl isothiocyanates with diaryliodonium salts is described. The reaction is performed under mild conditions and thiochromeno[2,3-b]indoles are obtained in moderate to good yields. This tandem protocol involves chemoselective S-arylation, regioselective 5-endo-trig cyclization and Friedel–Crafts-type cyclization processes. Two C–C bonds, one C–S bond, and two heterocyclic rings are formed in a single step. Preliminary mechanistic studies indicate that a carbocation mechanism is involved.

Synthesis of 6-Phosphorylated Phenanthridines by Mn(II)-Promoted Tandem Reactions of 2-Biaryl Isothiocyanates with Phosphine Oxides

A novel Mn(II)-promoted tandem phosphorylation/cyclization reaction of 2-biaryl isothiocyanates with phosphine oxides is described. This is the first general method to synthesize 6-phosporylated phenanthridines from 2-biaryl isothiocyanates. The approach is featured by oxidant-free, low loading of P-reagent, easy operation, and high functional group tolerance.

Yb(OTf)3 catalyzed [3 + 2] annulations of D–A cyclopropanes with β-oxodithioesters: a regioselective synthesis of tetrahydrothiophenes

A new route to prepare tetrahydrothiophene derivatives from D–A cyclopropanes and β-oxodithioesters catalyzed by Yb(OTf)3 is reported. This is the first example using β-oxodithioesters as dipolarophiles to react with D–A cyclopropanes. The method exhibits good regioselectivity.

A copper-catalyzed arylation/nucleophilic addition/fragmentation/C–S bond formation cascade: synthesis of bis(arylthio)imines

A new tandem arylation/nucleophilic addition/fragmentation/C–S bond formation reaction involving diaryliodonium salts as electrophiles was developed with Cu(OTf)2 as the catalyst. A series of unexpected bis(arylthio)imine derivatives were generated in good yields. The reaction proceeds under mild conditions, and the bis(arylthio)imines are readily transformed to other useful products.

Synthesis of 1-Thio-Substituted Isoquinoline Derivatives by Tandem Cyclization of Isothiocyanates

A copper-catalyzed tandem arylation-cyclization process to access 1-(arylthio)isoquinolines from isothiocyanates and diaryliodonium salts is described. It is the first general method to construct the potentially useful 1-(arylthio)isoquinoline derivatives. Moreover, 1-(methylthio)isoquinoline derivatives were also achieved successfully with MeOTf instead of diaryliodonium salts under metal-free conditions. Mechanistic studies reveal that these two processes proceed in different routes. This method has been successfully applied to the synthesis of quinazolinone alkaloid rutaecarpine.

Acid/base-controlled chemodivergent synthesis of two differently functionalized tetrahydroimidazo[1,2-a]pyridines

A new approach for the facile chemodivergent synthesis of tetrahydroimidazo[1,2-a]pyridines from β-ketothioamides, aldehydes and heterocyclic ketene aminals is described. In the presence of a base, an unprecedented ring-opening, tautomerization, recyclization cascade is observed and H2S eliminated tetrahydroimidazo[1,2-a]pyridines were formed in good yields. With catalytic amounts of acid, another type of different substituted tetrahydroimidazo[1,2-a]pyridines were obtained through dehydration.

Acid-promoted rapid solvent-free access to substituted 1,4-dihydropyridines from β-ketothioamides

β-Ketothioamides (KTAs) have been used as building blocks with aldehydes and β-enaminonitriles for synthesis of 1,4-dihydropyridines in the presence of AcOH under solvent-free conditions within 5 min. This new strategy exhibits remarkable features such as high chemoselectivity, mild reaction conditions, easily available substrates, and good yields.