Three-component coupling using arynes and aminosilanes for ortho-selective double functionalization of aromatic skeletons.

Arynes were found to couple with aminosilanes and carbonyl compounds in the presence of benzoic acid to provide 2-aminobenzhydrols. Sulfonylimines could also be applied to the reaction, enabling amino and aminomethyl moieties to be incorporated into contiguous positions of aromatic skeletons. Only a small amount of the three-component coupling product was obtained in the absence of benzoic acid, which confirms its vital role in the present reaction.

Insertion of arynes into carbon-halogen sigma-bonds: regioselective acylation of aromatic rings.

Arynes were found to insert into carbon-halogen sigma-bonds of various acid halides, enabling acyl and halogen moieties to be introduced simultaneously into adjacent positions of aromatic rings.

Three-component coupling of arynes, aminosilanes, and aldehydes.

A three-component coupling of arynes, aminosilanes, and aldehydes enables diverse amino and hydroxymethyl groups to be incorporated directly into 1,2-positions of aromatic rings.

Straightforward construction of diarylmethane skeletons via aryne insertion into carbon-carbon sigma-bonds.

Two molar amounts of arynes were found to couple with nitriles via carbon-carbon sigma-bond cleavage, assembling diverse diarylmethane skeletons in a straightforward manner.

CO2 incorporation reaction using arynes: straightforward access to benzoxazinone.

A zwitterion, generated from an aryne and an imine, has been demonstrated to serve as an excellent molecular scaffold for capturing CO2, which results in the straightforward formation of diverse benzoxazinones.

Palladium-catalyzed distannylation of ortho-quinodimethanes.

An exo-diene moiety of various ortho-quinodimethanes, regardless of its transient character, was inserted into a Sn-Sn sigma-bond of hexabutyldistannane in the presence of a palladium catalyst, giving alpha,alpha'-bis(tributylstannyl)-o-xylenes straightforwardly.

Singlet energy migration along an alternating block copolymer of oligothiophene and oligosilylene in solution.

The singlet excited-state properties of the block copolymers of oligothiophene and oligosilylene in solution were investigated with several fast spectroscopic methods. Time-resolved fluorescence measurements at room temperature and in a glassy matrix revealed that the singlet excited states of the block copolymers are deactivated accompanying structural changes of the polymer. It became clear from the transient absorption spectroscopy that the absorption peak of the singlet excited state shifted to the longer wavelength side compared to that of the corresponding oligothiophenes because of the sigma-pi conjugation of the oligothiophene and oligosilylene. The intersystem crossing process generating the triplet excited state was also revealed by the transient absorption spectroscopy. Energy migration along the polymer chain was revealed by the fluorescence anisotropy measurements. The time constant for the energy migration became faster as the size of the oligothiophene in the polymer repeating unit became shorter. From comparison with the Förster theory, the energy migration process was attributed to an incoherent hopping mechanism.

Palladium-catalysed dimerisation-distannylation of arynes: synthesis and reaction of 2,2'-distannylbiaryls.

Two molar amounts of arynes were found to insert into a Sn-Sn bond of a distannane in the presence of a sub-stoichiometric amount of a palladium-phosphite complex, affording straightforwardly 2,2'-distannylbiaryls.

Aminosilylation of arynes with aminosilanes: synthesis of 2-silylaniline derivatives.

The nitrogen-silicon sigma-bond of aminosilanes added across the triple bond of arynes to give varied 2-silylaniline derivatives straightforwardly.

Facile insertion reaction of arynes into carbon-carbon sigma-bonds.

The carbon-carbon sigma-bond of various beta-dicarbonyl compounds was found to add to the triple bond of arynes under extremely mild conditions, leading to direct introduction of different carbon functional groups into the aromatic skeletons.

Influences of self-assembled structure on mobilities of charge carriers in pi-conjugated polymers.

Mobilities of charge carriers in cast and spun films of poly(3-hexylthiophene)s (PHTs) with regioregularities of 97%, 81%, 70%, and 54% (denoted as PHT97%, PHT81%, PHT70%, and PHT54%, respectively) are evaluated as a function of doping level. A common feature of mobility vs doping level plots for all the PHT films is that the mobility decreases initially with the increase of the doping level and then starts to rise drastically at ca. 1% doping level. No large mobility difference is observed between cast and spun films of each PHT. In contrast, the difference in regioregularity of PHT resulted in a large mobility difference, especially in the low doping regime. At the highest doping levels of ca. 20%, the apparent mobility values reach 0.4 and 0.01 cm(2) V(-1) s(-1) for the cast films of PHT97% and PHT54%, respectively. These features of the mobility plots are discussed in connection with self-assembled structures of PHT films studied by electrochemical, in-situ ESR, in-situ UV-vis-NIR, and X-ray diffraction measurements. It is concluded first that mobilities of polarons are mainly controlled by the rate of an interchain charge hopping and second that the evolution of metallic conduction featured by the sharp mobility increase is irrelevant to the interchain stacking, or rather governed by an intrachain route.

A 2:1 coupling reaction of arynes with aldehydes via o-quinone methides: straightforward synthesis of 9-arylxanthenes.

[reaction: see text] A novel coupling reaction, where an aldehyde and two molar amounts of an aryne are assembled selectively, has been demonstrated to afford diverse 9-arylxanthene derivatives in one step. o-Quinone methide arising from the [2 + 2] cycloaddition of an aldehyde with an aryne was postulated as a transient intermediate.

Thiostannylation of arynes with stannyl sulfides: synthesis and reaction of 2-(arylthio)arylstannanes.

Arynes were found to insert into a sulfur-tin sigma-bond of stannyl sulfides to give a variety of 2-(arylthio)arylstannanes, whose carbon-tin bonds were applicable to further transformations.

Palladium-catalyzed bissilylation of arynes with cyclic disilanes: synthesis of benzo-annulated disilacarbocycles.

Arynes, generated in situ from 2-(trimethylsilyl)aryl triflate and a fluoride ion, were found to insert into a silicon-silicon bond of cyclic disilanes in the presence of a catalytic amount of a palladium-tert-alkyl isocyanide complex to afford diverse benzo-annulated disilacarbocycles straightforwardly in modest to high yields.

Facile synthesis of N-alkyl-N'-arylimidazolium salts via addition of imidazoles to arynes.

[reaction: see text] A novel synthetic approach to N-alkyl-N'-arylimidazolium salts has been developed on the basis of addition of imidazoles to arynes. A variety of N-alkyl-N'-arylimidazolium salts can be synthesized straightforwardly in modest to good yields. Furthermore, utility of the resulting imidazolium salts has been demonstrated by the palladium-catalyzed Suzuki-Miyaura coupling of aryl chlorides.

Ring-opening reactions of cyclic acetals and 1,3-oxazolidines with halosilane equivalents.

Reactions of acetal and 1,3-oxazolidine rings were examined using two kinds of iodosilane equivalent reagents, a 1:2 mixture of Me3SiNEt2 and MeI (reagent 1a) and a 1:1 mixture of Et3SiH and MeI containing a catalytic amount of PdCl2 (reagent 1b). In the reactions of alkanone ethylene acetals with reagent 1a, a C-O bond in the acetal ring readily cleaved to give 2-(trimethylsiloxy)ethyl enol ethers. Similarly, the C-O bond of 1,3-oxazolidine rings cleaved to give ring-opened imine or enamine derivatives. The reactions of aromatic ketone ethylene acetals and cyclohexanone trimethylene acetal led to deprotection of the acetal unit to liberate free ketones. With reagent 1b, cycloalkanone ethylene acetal afforded a dimeric product with 2-iodoethyl alkenoate moieties, while aromatic ketone ethylene or trimethylene acetals produced deprotected ketones.

Preparation of 4,4-diaryl-2-(tricyanoethenyl)dithienosiloles and vapor-chromic behavior of the film.

[reaction: see text] Reactions of 4,4-diphenyl- and 4,4-di(p-tolyl)dithienosilole with tetracyanoethene (TCNE) in DMF gave coupling products 4,4-diphenyl- and 4,4-di(p-tolyl)-2-(tricycanoethenyl)dithienosilole (1a and 1b) in good yield. The films of 1b exhibited vapor-chromism, and the color of the film changed from red to blue-purple upon exposure to the vapor of organic solvents such as ethanol, methanol, acetonitrile, ethyl acetate, acetone, and hexane. The color reverted to the original red upon contact with chloroform vapor, indicating that this process is reversible.

Ring-opening iodo- and bromosilation of lactones for the formation of silyl haloalkanoates.

Ring-opening halosilation of lactones with two types of reagents, Et(3)SiH/MeI(PdCl(2)) (1a) and Et(3)SiH/AllylBr(PdCl(2)) (1b), was studied. Cyclic esters such as gamma-butyrolactones, delta-valerolactone, and 6-hexanolide reacted with 1 equiv of 1a,b to give triethylsilyl omega-iodo- and omega-bromoalkanoates in good yields. Reaction of an acyclic ester, methyl benzoate, with 1a afforded triethylsilyl benzoate. O-Silyl-protected amino acids could be obtained by amination of the halosilation products, triethylsilyl omega-bromoalkanoates.