Synthesis of thiophene/phenylene co‐oligomers. I. Phenyl‐capped oligothiophenes

We report the synthesis of phenyl‐capped oligothiophenes via improved synthetic schemes. These schemes are based on the Grignard coupling reaction and enable us to obtain the target compounds at high yields. The resulting materials have been fully characterized through nmr and ir spectroscopies. The ir analysis is particularly useful in characterizing the materials of higher molecular weight, since those materials are difficult to dissolve in organic solvent. We also show an improvement on preparation of halogenated (oligo)thiophenes that are used as intermediates for synthesizing the target compounds. An alternative synthetic route to the phenyl‐capped oligothiophenes that utilizes the Suzuki coupling reaction is presented as well.     

Synthesis of thiophene/phenylene co‐oligomers. II [1]. Block and alternating co‐oligomers

We report the synthesis of block and alternating thiophene/phenylene co‐oligomers that is based either on the Suzuki coupling reaction or on the Grignard reaction. These reaction schemes enable us to obtain the target compounds at reasonably high yields. The resulting materials have been fully characterized through the solid‐state ¹³C nmr and Fourier‐transform ir as well as the ¹H nmr. Of these, the solid‐state ¹³C nmr and ir are particularly useful in characterizing the materials of higher molecular weight, since those materials are difficult to dissolve in organic solvents.     

Synthesis of thiophene/phenylene co‐oligomers. IV. 6‐ to 8‐ring molecules

We report the synthesis of various thiophene/phenylene co‐oligomers with a total number of thiophene and benzene (phenylene) rings of 6 to 8. These compounds include a phenyl‐capped sexithiophene, a thienyl‐capped quaterphenylene, as well as block and alternating co‐oligomers. The synthesis is based on either the Suzuki coupling reaction or the direct dimerization coupling. The latter method produces symmetric molecules with an even total ring number. These reaction schemes enabled us to obtain the target compounds in high quality. Although the resulting materials are difficult to dissolve in organic solvents and therefore difficult to identify by usual ¹H nmr spectroscopy, they have successfully been identified through Fourier‐transform ir spectroscopy. The specific group frequencies of ring‐stretching and out‐of‐plane deformation modes are characteristic of the substitution pattern of the individual thiophene and benzene rings.     

Studies with 1‐functionally substituted alkylbenzotriazoles: An efficient route for the synthesis of 1‐azolylbenzotriazoles,benzotriazolylazines and benzotriazolylazoloazines

A new approach to the synthesis of pyrazole, isoxazole, pyridine and pyrazolo[1,5‐α]pyrimidine deriva tives is reported. The structure of the newly synthesized compounds was elucidated by elemental analyses, ir and ¹H nmr spectra, and in some cases by ¹³C nmr investigation.     

A convenient,rapid, and highly selective method for synthesis of new pyrazolo[1,5‐a]pyrimidines via the reaction of enaminones and 5‐amino‐1H‐pyrazoles under microwave irradiation

Twelve new 7‐aryl‐3‐cyanopyrazolo[1,5‐a]pyrimidines ( 3a‐f ) and ethyl 7‐arylpyrazolo[1,5‐a]pyrimidine‐3‐carboxylates ( 3g‐l ) have been conveniently synthesized by the reaction of enaminones with 5‐amino‐1H‐pyrazoles in good yields under microwave irradiation. With one substituded enaminone, only one regioiso‐mer was obtained. The structures of new compounds were fully confirmed by elemental analysis, ir, ¹H nmr and X‐ray diffraction (XRD) analysis. A plausible reaction mechanism for the synthesis of title compounds is presented. The antifungal activities of some compounds are also reported.     

Three‐Ring‐Based Room‐Temperature Bent‐Core Nematic Compounds: Synthesis and Characterization

We report the synthesis and characterization of a new class of achiral three‐ring bent‐core compounds with an amide and ester linkage at the molecular bend, which are shown to exhibit nematic/phases in wide temperature ranges around room temperature (RT) and undulated SmC phases below RT. In contrast to previous studies, the compounds reported in this Communication show a true RT nematic phase with fluid physical appearance. They show strong photoluminescence in the mesophase and are found to display a one‐dimensional array of intermolecular hydrogen bonding. Furthermore, the nematic phases exhibited by these compounds show a good homeotropic alignment that can be exploited in applications such as optics and sensing. Considering the scarcity of bent‐core materials exhibiting an RT nematic mesophase, this new class of materials is promising.     

Synthesis and spectral properties of 7‐chloro‐5‐[(o‐ and p‐R1)phenyl]‐1‐R2‐3H‐[1,4]benzodiazepin‐2‐ones

A series of twelve new 7‐chloro‐5‐[(o‐ and p‐R₁)phenyl]‐1‐R₂‐3H‐[1,4] benzo‐diazepin‐2‐ones, which have possible pharmacological properties were synthesized. The synthesis of all the final compounds was carried out by four steps. The structure of all final products was corroborated by ir, ¹H nmr, ¹³C nmr and ms, and have been obtained in 35‐94% yield.     

Ring Expansion to 6‐, 7‐, and 8‐Membered Benzosilacycles through Strain‐Release Silicon‐Based Cross‐Coupling

The synthesis of silacycles is highly appealing due to their important applications in organic synthesis, medicinal chemistry, and materials chemistry. However, sila‐tetralins and sila‐benzosuberanes are surprisingly under‐represented due to a lack of general methods to access these compounds. We successfully developed a Pd‐catalyzed strain‐release silicon‐based cross‐coupling as an unprecedented ring‐expansion method, which constitutes a general route for preparing diverse sila‐tetralins and sila‐benzosuberanes.     

Synthesis of thiophene/phenylene co‐oligomers. V. Functionalization at molecular terminals toward optoelectronic device applications

We report the synthesis of various thiophene/phenylene co‐oligomers with a total number of thiophene and benzene (phenylene) rings of 5 and 6 with various terminal groups. Those terminal groups have been chosen from among alkyl groups, methoxy groups, trifluoromethyl groups, and cyano groups. The molecular backbone of these compounds comprises phenyl‐ or biphenylyl‐capped thiophene (or oligothiophene) or an alternating co‐oligomer. The synthesis is based on either the Suzuki coupling reaction or the Negishi coupling reaction. These reaction schemes enabled us to obtain the target compounds in high quality. In particular, the latter coupling method turned out to produce the compounds at a high yield. The terminal groups are expected to produce various functionalities based upon their electron donating character (alkyl groups and methoxy groups) or electron withdrawing character (trifluoromethyl groups and cyano groups). Additionally some of these groups bring about enhanced solubility. This will lead to the production of a diversity of modified compounds of thiophene/phenylene co‐oligomers. To give an example that demonstrates usefulness of the target compounds, we present optoelectronic data that are associated with their device applications.     

Insertion of Isolated Alkynes into Carbon–Carbon σ‐Bonds of Unstrained Cyclic β‐Ketoesters via Transition‐Metal‐Free Tandem Reactions: Synthesis of Medium‐Sized Ring Compounds

The transition‐metal‐free insertion of isolated alkynes into carbon–carbon σ‐bonds of unstrained cyclic β‐dicarbonyl compounds has been reported. These tandem reactions offer an efficient synthesis of medium‐sized ring or fused‐ring compounds through ring expansion. The methodology has the potential to be widely used throughout organic synthesis due to the easily accessible starting materials and mild reaction conditions.     

Platinum‐Catalyzed Domino Reaction with Benziodoxole Reagents for Accessing Benzene‐Alkynylated Indoles

Indoles are omnipresent in natural products, bioactive molecules, and organic materials. Consequently, their synthesis or functionalization are important fields of research in organic chemistry. Most works focus on installation or modification of the pyrrole ring. To access benzene‐ring‐functionalized indoles with an unsubstituted pyrrole ring remains more challenging. Reported herein is a platinum‐catalyzed cyclization/alkynylation domino process to selectively obtain C5‐ or C6‐functionalized indoles starting from easily available pyrroles. The work combines, for the first time, a platinum catalyst with ethynylbenziodoxole hypervalent iodine reagents in a domino process for the synthesis of polyfunctionalized arene rings and gives access to important building blocks for the synthesis of bioactive compounds and organic materials.     

Substituted 4‐Oxo‐1,2,3,4‐tetrahydroquinoline‐3‐carboxylic Esters by a Tandem Imine Addition‐SNAr Reaction

A tandem imine addition‐S_NAr annulation reaction has been developed as a new approach to the synthesis of 4‐oxo‐1,2,3,4‐tetrahydroquinoline‐3‐carboxylic esters. A series of these structures has been generated by reacting selected imines with tert‐butyl 2‐fluoro‐5‐nitrobenzoylacetate. Structural variations in the final products are accomplished by changing the substituents on the imine and the alkyl group of the ester. The title compounds are isolated as their enols in 55–97% yield without the need for added base or catalysts. The synthesis of the starting materials as well as mechanistic studies and further synthetic conversions of the products are presented.     

KIT‐6 Mesoporous Silica‐coated Magnetite Nanoparticles: A Highly Efficient and Easily Reusable Catalyst for the Synthesis of Benzo[d]imidazole Derivatives

KIT‐6 mesoporous silica‐coated magnetite nanoparticles as highly ordered large‐pore nanoparticles supply an environmentally friendly procedure for the synthesis of benzo[d]imidazoles through condensation of 1,2‐diaminobenzene with aryl aldehydes. These compounds were obtained in high yields and short reaction times. The catalyst could be easily recovered using an external magnet and reused for six cycles with almost consistent activity. All of the synthesized compounds were characterized by their physical constant, comparison with authentic samples, ir, 1H nmr, 13C nmr spectroscopy, and elemental analysis.     

Synthesis of 5‐substituted 2‐(2,4‐dihydroxyphenyl)‐1,3,4‐thiadiazoles

One‐stage synthesis of 5‐substituted (alkyl, aryl, heteroaryl, arylalkyl, heteroalkyl, alkoxy‐, aryloxy)‐2‐(2,4‐dihydroxyphenyl)‐1,3,4‐thiadiazoles is described. The compounds were prepared by the reaction of sulfinyl‐bis(2,4‐dihydroxythiobenzoyl) (STB) with hydrazides or carbazates. The structure of new compounds was assigned by ir, nmr and ms data.     

Palladium(II)‐Catalyzed meta‐CH Olefination: Constructing Multisubstituted Arenes through Homo‐Diolefination and Sequential Hetero‐Diolefination

Divinylbenzene derivatives represent an important class of molecular building blocks in organic chemistry and materials science. Reported herein is the palladium‐catalyzed synthesis of divinylbenzenes by meta‐C? H olefination of sulfone‐based arenes. Successful sequential olefinations in a position‐selective manner provided a novel route for the synthesis of hetero‐dialkenylated products, which are difficult to access using conventional methods. Additionally, 1,3,5‐trialkenylated compounds can be generated upon successful removal of the directing group.     

One‐Pot Synthesis of 3‐Cyano‐2‐pyridones

A versatile synthesis of 3‐cyano‐2‐pyridones via a one‐pot, four‐component condensation of ethyl cyanoacetate, ketones, aldehydes, and ammonium acetate under very mild conditions has been developed. This method provides rapid access to this type of valuable heterocyclic compounds from readily available materials in a single operation.     

Antimony‐Functionalized Phosphine‐Based Photopolymer Networks

The synthesis of phosphane‐ene photopolymer networks, where the networks are composed of crosslinked tertiary alkyl phosphines are reported. Taking advantage of the rich coordination chemistry of alkyl phosphines, stibino‐phosphonium and stibino‐bis(phosphonium) functionalized polymer networks could be generated. Small‐molecule stibino‐phosphonium and stibino‐bis(phosphonium) compounds have been well characterized previously and were used as models for spectroscopic comparison to the macromolecular analogues by NMR and XANES spectroscopy. This work reveals that the physical and electronic properties of the materials can be tuned depending on the type of coordination environment. These materials can be used as ceramic precursors, where the Sb‐functionalized polymers influence the composition of the resulting ceramic.     

Palladium(II)‐Catalyzed meta‐C?H Olefination: Constructing Multisubstituted Arenes through Homo‐Diolefination and Sequential Hetero‐Diolefination

Divinylbenzene derivatives represent an important class of molecular building blocks in organic chemistry and materials science. Reported herein is the palladium‐catalyzed synthesis of divinylbenzenes by meta‐C H olefination of sulfone‐based arenes. Successful sequential olefinations in a position‐selective manner provided a novel route for the synthesis of hetero‐dialkenylated products, which are difficult to access using conventional methods. Additionally, 1,3,5‐trialkenylated compounds can be generated upon successful removal of the directing group.     

Transition‐Metal‐Catalyzed CS Bond Coupling Reaction

Sulfur‐containing molecules such as thioethers are commonly found in chemical biology, organic synthesis, and materials chemistry. While many reliable methods have been developed for preparing these compounds, harsh reaction conditions are usually required in the traditional methods. The transition metals have been applied in this field, and the palladium‐catalyzed coupling of thiols with aryl halides and pseudo halides is one of the most important methods in the synthesis of thioethers. Other metals have also been used for the same purpose. Here, we summarize recent efforts in metal‐catalyzed C? S bond cross‐coupling reactions, focusing especially on the coupling of thiols with aryl‐ and vinyl halides based on different metals.     

Studies on the synthesis of heterocyclie compounds. II. Synthesis of 2,2-disubstituted-1,3-benzoxathioles

The condensation of 2-hydroxythiophenol (I) with acetylenic compounds (IIa-g) or halo-genated esters (IV, V, VIa and b) led to the synthesis of 2,2-disubstituted-1,3-benzoxathioles (IIIa-g). The structures of these compounds were established by elemental analysis and by ir and nmr spectra.