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Much interest has been paid to cyclic diaryliodonium salts as bis(electrophile)s in transition-metal-catalyzed annulation reactions to produce polycyclic (hetero)aromatic hydrocarbons. Herein, we report that dibenziodolium triflates smoothly react with potassium thioacetate in the presence of CuCl2 in THF or DMSO at 100–110 °C to afford the corresponding dibenzothiophenes in good-to-high yields. The coupling reaction tolerates reactive functional groups such as chloro and cyano and serves as a facile and reliable method for the synthesis of unsymmetrical dibenzothiophenes.

The construction of a diorganosilylene bridge over a biaryl moiety at the 2,2′-positions is a versatile strategy for fine-tuning its HOMO–LUMO energy gap, which is closely linked to the electronic and optical properties of the compounds. Therefore, there is growing interest in the use of silicon-bridged biaryl motifs as key cores of various types of advanced functional materials, such as light-emitting, semiconducting, photovoltaic, and sensing materials. To accelerate the advances of materials based on silicon-bridged biaryls, it is essential to create new classes of biaryls and explore their functions and properties. This Personal Account describes recent research on the development of organic chromophores based on functionalized dibenzosiloles and 12H-indololo[3,2-d]naphtho[1,2-b][1]siloles as solid-state emitters.

The dehydrogenative coupling of maleic acids with alkynes proceeds smoothly accompanied by decarboxylation under rhodium catalysis to produce variously substituted α-pyrone derivatives. The catalyst system is also applicable to the coupling with 1,3-diynes and alkenes.

A novel binuclear phthalocyanine tweezers, in which two zinc-phthalocyanine rings are linked to an optically active binaphthyl group through triazolyl linkages, was self-cyclized through triazolyl-to-zinc coordination bonds. An axially chiral S -binaphthyl group induced planar chirality in a slipped-cofacial stack of phthalocyanine moieties, and therefore displayed fluorescence with a good quantum yield ( Φ F = 0.23) and circularly polarized luminescence with a moderate intensity of dissymmetry factor ( g lum = −4 × 10 −4 ) in the near-infrared wavelength region.

This microreview describes our contributions to the development of palladium-catalyzed annulations of organodimetallic reagents with organic dihalides, which serve as versatile synthetic methods for functionalized polycyclic aromatic hydrocarbons. Presented first are palladium-catalyzed double cross-coupling reactions of 1,2-diborylalkenes and -arenes with 2,2′-dibromobiaryls and 1-bromo-2-(2-bromoethenyl)arenes, respectively. The next section describes palladium-catalyzed coupling reactions between 9-stannafluorenes and 1,2-dibromoarenes, in which the 9-stannafluorenes act as equivalents of 1,4-dimetal reagents. The last section covers palladium-catalyzed double cross-coupling reactions variously between 1,2-diboryl reagents and 1-bromo-2-(bromomethyl)arenes, between 1,1-diborylalk-1-enes and 2,2′-dibromobiaryls, and between 9-stannafluorenes and 1,1-dibromoalk-1-enes, to form systems containing five-membered rings in one-step fashion.

Palladium-catalyzed double cross-coupling reactions of 1,1-bis(pinacolato)borylalk-1-enes with 2,2′-dibromobiaryls and of 9-stannafluorenes with 1,1-dibromoalk-1-enes have been demonstrated to serve as new synthetic methods for dibenzofulvenes.

(Z)-1,2-Diaryl-1,2-bis(pinacolatoboryl)ethenes underwent double-cross-coupling reactions with 1-bromo-2-[(Z)-2-bromoethenyl]arenes in the presence of [Pd(PPh(3))(4)] as a catalyst and 3 M aqueous Cs(2)CO(3) as a base in THF at 80 °C. The double-coupling reaction gave multisubstituted naphthalenes in good to high yields. Annulation of 1,2-bis(pinacolatoboryl)arenes with bromo(bromoethenyl)arenes in the presence of a catalyst system that consisted of [Pd(2)(dba)(3)] (dba=dibenzylideneacetone) and 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (SPhos) under the same conditions produced fused phenanthrenes in good to high yields. The first annulation coupling occurred regiospecifically at the bromoethenyl moiety. This procedure is applicable to the facile synthesis of polysubstituted anthracenes, benzothiophenes, and dibenzoanthracenes through a double annulation pathway by using the corresponding dibromobis[(Z)-2-bromoethenyl]benzenes as diboryl coupling partners.

This study demonstrates that the double cross-coupling reaction of 1,2-bis(pinacolatoboryl)alkenes and -arenes with 2,2′-dibromobiaryls proceeds smoothly with the aid of a catalytic amount of Pd(PPh3)4 in the presence of excess base to give a variety of polycyclic aromatic hydrocarbons, such as phenanthrenes, [5]helicene, dithienobenzenes, triphenylenes, dibenzo[g,p]chrysenes, and triphenyleno[1,2-b:4,3-b′]dithiophenes in good to high yields. It is noteworthy that the annulations using 2,2′-dibromooctafluorobiphenyl as an electrophile furnish the otherwise difficult to synthesize octafluorophenanthrenes and semi-fluorinated dibenzo[g,p]chrysenes in high yields.

There has been extensive research on the development of organic optoelectronic devices, such as organic light-emitting diodes, organic field-effect transistors, and organic solid-state lasers from various viewpoints, ranging from basic studies to practical applications. As organic materials are used as solids in these devices, the importance of organic chromophores that exhibit intense emissions of visible light in the solid state is greatly increasing in the field of organic electronics. However, highly efficient emission from organic solids is very difficult to attain because most organic emitting materials strongly tend to cause concentration quenching of the luminescence in the condensed phase. Therefore, in order to generate and improve organic optoelectronic devices, it is necessary to design novel chromophores that exhibit superior solid-state emission performance. This Focus Review covers the recent development of highly emissive organic small molecules whose photoluminescence quantum yields in the solid state have been reported. Following the introduction, the photophysical processes of excited molecules are briefly reviewed. Subsequently, organic solid fluorophores are described with an emphasis on the characteristics of their molecular structures.

A highly regio- and sterecontrolled glyoxylate-ene reaction with allylic and homoallylic ethers has been developed, which allows regio- and stereospecific multifunctionalizations as highlighted by a short synthesis of (±)-avenaciolide

Several excellent methods have been devised for acyclic stereocontrol over 1, 2- and 1, 3-asymmetric relationships. However, approaches to control remote 1, >3-relationships are rare. Hence the development of methods for remote stereocontrol has remained as one of the most challenging problems in organic synthesis. The methods for remote stereocontrol are conceptually divided into six different types; (a) “coupling” of chiral synthons; (b) “removal” of chiral centers from a chiral pool to keep the remote chiral centers; (c) “chirality transfer” of the adjacent chiral center (temporarily introduced) to the remote position by sigmatropic rearrangements or stereospecific substitution reactions with organometallic reagents; (d) “asymmetric synthesis” without any communication of the pre-existing chiral center; (e) “relative asymmetric induction” with stereo-communication of the pre-existing chiral center; (f) “internal asymmetric induction” over the new and remote chiral centers during C-C bond formation. The last two methodologies are relatively new comers and hence this review is focused on these two methodologies which are based on chelation control, vinylogous stereoelectronic (Cram's) control, neighboring group participation, orbital control, and so forth.

A new approach to remote asymmetric induction is described for not only a 1,4- but also a 1,5-relationship, which is based on the carbonyl-ene reactions with chiral bishomoallylic silyl ethers. Silyl ethers, rather than alkyl ethers, exhibit β-regiospecificity. Remarkably high levels of remote asymmetric induction can then be established with chiral bishomoallylic ethers to provide eventually a simple and efficient method for asymmetric induction

A novel route to substituted tetrahydrofurans is described, which is based on the Lewis acid-promoted Prins cyclization with side chain formation of carbon-carbon bond. Bishomoallylic silyl ethers, rather than the (chloro)benzyl ethers and esters, provide selectivity tetrahydrofurans, indicating the siloxy effect for facilitating the cyclization.

Incorporation of the title polysilacage moiety into chromophores such as biphenyl, terphenyl, stilbene and tolan is found to induce bathochromic shifts of absorption and fluorescence spectra as well as enhancements of molar extinction coefficients and fluorescence quantum yields.

A new method for the synthesis of the 1,3-disilacyclohexane skeleton is established involving silylation of a dithioacetal followed by ring closure with a base. The spiro-fused disilacyclohexane ring is shown to be structurally strain-free, like cyclohexane, on the basis of its X-ray analysis. The reaction mechanism involving a silacyclopropane intermediate is proposed.

The reagent consisting of 70% HF–py (py = pyridine) and a halonium oxidant converts R–OCS 2 Me into either R–OCF 3 (R = primary) or R–F (R = secondary, tertiary or benzylic) whereas the 50% HF–py system converts R–OCS 2 Me (R = secondary) into R–OCF 3 .

Treatment of RCH(OMEM)CFBr2 with n-BuLi at −130 °C in the presence of 4-heptanone gives the corresponding adduct diastereoselectively. The stereochemical outcome is explained in terms of the chelation between lithium and oxygen atoms of the MEM group. Starting with 2-phenylpropanal, a product is produced highly selectively containing three contiguous stereocenters including a -CFBr- moiety.

The title carbenoid reagent was generated by treatment of dibromofluoromethyl( t -butyl)dimethylsilane with butyllithium in THF at −78 °C and was allowed to react with aldehydes and ketones to give 1-fluoro-1-silyloxiranes in good yields. Alkylation of the silyl-substituted carbenoid was also achieved efficiently in good yields.

A convenient synthetic method is described for new type liquid crystals (LCs) containing a cyclohexyl trifluoromethyl ether moiety. The novel LCs are shown to exhibit mesophases and decrease birefringence and threshold voltage of host LCs upon mixing by 20 wt%.

Bis[bis(methylthio)lithiomethyl]dimethylsilane was generated from bis[bis(methylthio)methyl]dimethylsilane by deprotonation with t-BuLi in THF and allowed to react with various dichloro(poly)silanes to give the corresponding 4- to 7-membered polysilacarbacycles in moderate to good yields. The methylthio groups in the cyclized products were readily removed by radical reduction with Bu3SnH.

The double alkylation of bis[2-(2-lithio-1,3-dithian)-yl]diorganosilane with bis(bromo-methyl)diorganosilanes proceeds smoothly in good yields in a mixture of THF-hexamethylphosphoric triamide (HMPA) or THF-1,1,3,3-tetramethylurea (TMU) to give 1,4-disilacyclohexanes whose conformation was shown to be a twist-boat on the basis of X-ray analysis.

The combination of the regioselective propiolate-ene reaction, catalytic enantioselective epoxidation and catalytic enantioselective carbonyl-ene cyclization completes the synthesis of the A ring of the hybrid 19-nor-22-oxa D3 analogue (1), which shows the significant activity in transactivation.

2,2,3,3,5,5,6,6,7,7,8,8-Dodecamethyl-2,3,5,6,7,8-hexasilabicyclo[2.2.2]octane (1) was synthesized for the first time via three steps in 56% overall yield through triple silylation with three dichlorodimethyldisilane molecules of two trianionic molecules derived from bis(phenylthio)methane. The molecular structure of 1 was shown to be slightly distorted from an ideal bicyclo[2.2.2]octane skeleton by X-ray analysis. The derivatization of 1 and UV spectra of those compounds are described.

The treatment of tribromofluoromethane with BuLi in THF–Et2O (2 : 1) at −130 °C generated dibromofluoromethyllithium, which was allowed to react smoothly with a coexisting aldehyde or ketone (RR′C=O) to give fluorinated alcohol RR′C(OH)CFBr2 (3) in good yield. Alcohol 3 was converted stereoselectively to (E)-1-bromo-1,2-difluoro olefin 5 via fluorination with Et2NSF3, followed by dehydrobromination with lithium 2,2,6,6-tetramethylpiperidide, while (E)-1-bromo-1-fluoro olefin was obtained with high selectivity by acetylation of 3, followed by reductive elimination using EtMgBr/(i-Pr)2NH. Difluoro olefin 5 underwent a cross-coupling reaction with an aryl, alkenyl, or alkynylmetal reagent to afford the corresponding fluoro olefin with retention of configuration. On the other hand, the treatment of RCH[OCH2O(CH2)2OCH3]CFBr2 with BuLi at −130 °C in the presence of 4-heptanone gave the corresponding adduct diastereoselectively. The stereochemical outcome is explained in terms of chelation between lithium and ox...

Reaction of fluorotris(trimethylsilyl)methane and aldehydes is catalyzed by KF/18-Cr-6 to give 1,3-disubstituted 2-fluoro-2-propen-1-ols in one pot. On the other hand, SnLi exchange of bis(trimethylsilyl)-fluoro(tributylstannyl)methane with BuLi and subsequent treatment with an aldehyde afforded 1-fluoroalkenyltrimethylsilanes in moderate to good yields.

Treatment of 1,1-(bis(pinacolato)boryl)alkenes with ex- cess of 1-bromo-1-lithioethene was found to give 2,3-bis((pinacola- to)boryl)-1,3-dienes in moderate to good yields. Synthetic applications of 2,3-(bis(pinacolato)boryl)-1,3-butadiene were also demonstrated.

Phenyl groups were successively introduced at the bridgehead positions of cage compound HC(SiMe2SiMe2)3CH via deprotonation–cyclohexenylation–dehydrogenation. UV absorption spectra of the cage compounds suggested the possibility of electronic interaction between the cage and aromatic moieties. Bromination of the phenylated cage molecule gave a p-bromo derivative that was transformed to liquid crystalline compounds.

Silylboryl reagents for organic synthesis: 1-silyl-1-boryl-2-alkenes (2) were prepared efficiently by gem-silylborylation of α-chloroallyllithium compounds from (dimethylphenylsilyl)(pinacolato)borane (1; see scheme, LDA=lithium diisopropylamide) and were demonstrated to allylate acetals and aldehydes in the presence of a Lewis acid to produce (E)-4-alkoxy-alkenylboronates. Heating the reagents with aldehydes in the absence of Lewis acid afforded (Z)-4-hydroxy-alkenylsilanes stereospecifically.

Novel synthetic reagents with gem-silylboryl and gem-diboryls have been prepared through formation of an ate complex from a lithium carbenoid and an interelement compound such as (dimethylphenylsilyl) (pinacolato) borane or bis (pinacolato) diboron, followed by 1, 2-migration of the silyl or boryl group from a negatively charged boron to the carbenoid carbon. Alkenylidene-type carbenoids afforded 1-boryl-1-silyl-1-alkenes and 1, 1-diboryl-1-alkenes, applicable to boron-mediated coupling reactions. Reaction of α-chloroallyllithiums with the silylborane gave 1-boryl-1-silyl-2-alkenes, which were shown to serve as a versatile reagent for stereodivergent allylation leading to 4-oxy-(E)-alkenylboronates and 4-oxy-(Z)- alkenylsilanes. 1-Boryl-1-silylallenes were synthesized from 3-acyloxy- or 3-chloroalkynyllithium and the silylborane. Furthermore, novel synthesis and application of 2, 3-diboryl-1, 3-dienes are presented.

Background: Since trifluoromethyl-containing compounds have found diverse applications in the fields of pharmaceuticals and agrochemicals, facile and selective synthetic methods for trifluoromethyl-substituted compounds are an essential tool for advanced medicinal chemistry. Now that diverse synthetic transformations of carbon–carbon triple bonds are available, 3,3,3-trifluoropropynyl-substituted compounds serve as versatile building blocks for target molecules containing trifluoromethyl groups. Thus, novel synthetic methods and reagents for incorporation of a 3,3,3-trifluoropropynyl group into an organic compound have been the major concern in exploration and modification of fluorine-based biologically active substances. Results & discussion: We report a preparative method of 3,3,3-trifluoropropynyllithium and its reaction with electrophiles including aldehydes, ketones, trimethoxyborane, chlorosilanes and chlorostannanes in detail. Palladium-catalyzed synthetic reactions of the carbonyl adducts and the ...

Palladium-catalyzed intramolecular direct arylation of 2-[(2-pyrrolyl)silyl]aryl triflates gives 3,2′-silicon-bridged 2-arylindoles and -pyrroles in good to high yields. The reaction proceeds through cleavage of C−OTf, C−Si, and C−H bonds to result in the formation of C−C and C−Si bonds. Various kinds of functional groups such as OMe, CN, Cl, F, and SiMe3 tolerated the conditions. The new reaction allows synthesis of functionalized Si-bridged 2-arylindoles that emit intense and efficient blue fluorescence in the solid state.

The direct oxidative coupling of 2-amino- and 2-hydroxybenzoic acids with internal alkynes proceeds efficiently in the presence of a rhodium/copper catalyst system under air to afford the corresponding 8-substituted isocoumarin derivatives, some of which exhibit solid-state fluorescence. Depending on conditions, 4-ethenylcarbazoles can be synthesized selectively from 2-(arylamino)benzoic acids. The oxidative coupling reactions of heteroarene carboxylic acids as well as aromatic diacids with an alkyne are also described.

Diverse kinds of gem- and vic-diborylated compounds are now readily available thanks to advances in gem-diborylation of lithium carbenoids as well as vic-diborylation of carbon-carbon multiple bonds with diboron compounds. These diborylated reagents lead to invention of polyborylated reagents and many novel and useful synthetic methods for supreme stereocontrol. This review summarizes preparative methods and synthetic reactions of di- and polyborylated reagents with the emphasis on multiple bond formation.

We describe here a facile route to 2-trifluoromethyl-substituted 4,5-dihydrooxepins, which involves stereoselective preparation and Cope rearrangement of 2-trifluoromethyl-cis-2,3-bis(alkenyl)oxiranes. Treatment of 1,1-dichloro-2-hydroxy-2-trifluoromethylalk-3-enes with alkenyllithium and then lithium 2,2,6,6-tetramethylpiperidide generated cis-2,3-bis(alkenyl)-2-lithio-3-trifluoromethyloxiranes, which reacted with a variety of electrophiles to give the corresponding tri- and tetrasubstituted oxiranes stereoselectively. Cope rearrangement of the cis-oxiranes proceeded upon heating, giving rise to 2-trifluoromethyl-substituted 4,5-dihydrooxepins in high to excellent yields. The Cope rearrangement is found remarkably accelerated by the presence of such metal substituents as boryl, silyl, and stannyl groups at 7-position, that can act as versatile functionalities for further elaboration of the ring-enlarged products. Subsequent reduction and oxidation of the rearranged products gave 2-trifluoromethylated oxepanes and oxepins in good yields.