Formation of Seven-Membered Carbocycles via 7-endo Mode Cyclization of Lithioheptatrienes.

The highly selective synthesis of triene derivatives was achieved by a zirconocene-mediated three-component coupling reaction, and the trienes were efficiently subjected to 7-endo mode cyclization. The reaction of unsymmetrical zirconacyclopentadienes prepared from two different alkynes with N-bromosuccinimide (NBS) followed by treatment with allyl halides in the presence of CuCl afforded the corresponding heptatrienes in good yields. When the trienes reacted with an organolithium reagent, 7-endo mode cyclization occurred smoothly to give the corresponding cycloheptadiene.

Dehydro side coupling of substituted pentacene derivatives.

1,2,3,4,8,9,10,11-Octaalkylpentacenes were synthesized in high yields from tetrahydropentacenes by the pentacene-DDQ adduct method in the presence of amine. Dehydro side-coupling reactions of pentacene derivatives proceeded to give the corresponding 6,6'-dipentacenyl derivatives in high yields in the presence of a catalytic amount of CSA and 0.5 equiv of DDQ. The structures of dehydro side-coupling products of substituted pentacenes were determined by NMR and X-ray analysis. The combination of acid and DDQ was necessary for the dehydro side coupling of substituted pentacenes.

Preparation of 6,13-bis(trimethylsilyl)pentacene and formation of second-ring Diels-Alder adduct of pentacene.

6,13-Bis(trimethylsilyl)pentacene was synthesized by a coupling reaction of bicyclic dilithiobutadiene with diiodonaphthalene followed by aromatization. Diels-Alder reaction of 6,13-bis(trimethylsilyl)pentacene with dienophiles afforded the corresponding second-ring adducts. Elimination of two silyl groups gave the second-ring Diels-Alder adducts of parent pentacene.

Synthesis of 1,2,3,4,8,9,10,11-octasubstituted pentacenequinone derivatives and their conversion into substituted pentacenes.

A series of 1,2,3,4,8,9,10,11-octasubstituted pentacenequinone derivatives were prepared by the oxidation of 1,2,3,4,8,9,10,11-octasubstituted pentacenes, which were synthesized by the double homologation method. Oxidation of the pentacenes was carried out with H(5)IO(6) or air and DDQ. These octasubstituted pentacenequinones were converted into 1,2,3,4,6,8,9,10,11,13-decasubstituted or 2,3,6,9,10,13-hexasubstituted pentacene derivatives by the introduction of aryl or alkynyl groups at the carbonyl carbons. The photophysical properties of these new pentacenes have been measured in solution, and the substituent effects are discussed.

Zirconium-mediated coupling reaction for synthesis of substituted thiophene-fused acenes.

A novel zirconium-mediated synthesis of substituted thiophene-fused acenes is described. A variety of substituents, such as alkyl, aryl, silyl, iodo, and alkynyl groups, could be introduced to the acene skeleton by this method. Moreover, the double coupling with tetraiodothiophene gave the corresponding dianthrathiophene.

Zirconium-mediated selective synthesis of 1,2,4,5-tetrasubstituted benzenes from two silyl-substituted alkynes and one internal alkyne.

Selective synthesis of 1,2,4,5-tetrasubstituted benzenes was achieved via formation of 2,5-bis(trimethylsilyl)zirconacyclopentadienes from 2 equiv of TMS-substituted alkynes with Cp(2)ZrBu(2) and Cu-mediated formation of 1,4-disilylbenzene by cycloaddition of zirconacyclopentadienes to disubstituted alkynes. Preparation of 1,2,3,4,9,10-hexasubstituted pentacene and 2,3,6,11-tetrasubstituted naphthacene derivatives were demonstrated by a homologation or coupling method using tetrasubstituted benzene.

Coupling of the R-Cp or indenyl ligand with the diene moiety of bis(substituted cyclopentadienyl)- or bis(indenyl)zirconacyclopentadienes.

When bis(substituted cyclopentadienyl)- or bis(indenyl)zirconacyclopentadienes were treated with TiCl(4), a coupling reaction between the substituted cyclopentadienyl or indenyl ligand and the diene moiety proceeded to give indene or fluorene derivatives in moderate to high yields. With the sterically hindered t-Bu-substituted Cp ligand, the coupling products were obtained in high yields.

Double homologation method for substituted soluble pentacenes and dimerization behaviours of pentacenes.

Double up: A zirconium-mediated double homologation method was successfully applied for the synthesis of multi-substituted pentacene derivatives from 1,2,4,5-tetrakis(propargyl)benzenes. The bis(zirconacyclopentadiene) intermediates were also characterized. Among these symmetrical derivatives, tetra- and octa-substituted pentacenes undergo reversible conversion between monomeric and dimeric forms. A double homologation method for the formation of substituted soluble pentacenes was developed by a zirconium-mediated cyclization of tetrayne derivatives. Thermal dimerization of tetra- and octasubstituted pentacenes was observed. The dimerization behavior was observed to be strongly related to the substituent groups affixed to the pentacenes.

Once cleaved C-C bond was reformed: reversible C-C bond cleavage of dihydroindenyltitanium complexes.

The once cleaved carbon-carbon bond of the Cp moiety in 2 was recombined in indene products. Aslo, we propose a novel mechanism for the cleavage of the carbon-carbon bond of the Cp moiety.

Selective linear triene formation from different alkynes using Zr/Cu system.

Selective synthesis of linear trienes from three different alkynes was achieved in one-pot procedure using the Zr/Cu system. Zirconacyclopentadiene prepared from two different alkynes such as an alkyl-substituted alkyne and an aryl-substituted alkyne reacted with NCS gave chlorodienylzirconocene. It reacted with the third alkyne with electron-withdrawing groups in the presence of CuCl to afford the corresponding linear triene.

Substituent effects in the preparation of naphthacenes by the coupling reaction of diyne-derived zirconacyclopentadienes with tetraiodobenzene.

The synthesis of a series of substituted naphthacene derivatives through the coupling reaction of zirconacyclopentadienes with diiodobenzenes is reported. A reaction of bis(propargyl)benzenes with zirconacene dibutyl afforded the corresponding tricyclic zirconacyclopentadienes, which reacted with o-diiodobenzenes to afford the corresponding dihydronaphthacenes. The yields of the coupling reactions were dependent on the substituents on both of the zirconacycles and o-diiodobenzenes. The reactions of diphenyl-substituted zirconacycles gave higher yields than those of the alpha,alpha'-dialkyl-substituted derivatives. The iodide functions thus introduced allowed further introduction of substituents by well-established cross-coupling reactions after construction of the naphthacene skeletons.

Isolation of 6,13-dipropylpentacene and its tautomerization.

6,13-Dipropyl-5,14-dihydropentacene was aromatized by the combination of the formation of pentacene-DDQ adduct and abstraction of DDQ from the pentacene-DDQ adduct with 50 equiv of gamma-terpinene to give 6,13-dipropylpentacene cleanly. It was stable and isolable. In the presence of a catalytic amount of acid, 6,13-dipropylpentacene was isomerized to its tautomer.

Carrier mobility for organic semiconductors: reduction of noise of the short part drift time in the time of flight mobility method.

Measurements of time of flight (TOF) mobility of organic semiconductors become difficult when the mobility values are high, since the electronic signals overlap with the noise of the short part in drift time. Such noise of the short part in the drift time in the TOF method for measurements of carrier mobility was reduced by three methods: (1) longer distance (3.5 m) between sample and the N(2) laser, (2) optical connection (photo coupler) between the N(2) laser and the pulse generator, and (3) using a digital filter to remove characteristic pulses caused by N(2) laser. Each method showed significant reduction of the noise. When all three methods were applied, 94% of the noise was reduced. The measurement of TOF mobility was demonstrated with TPD (N,N'-diphenyl-N,N'-di(meta-tolyl)benzidine) film. Electronic signals in TOF measurements were clearly observed and the TOF mobility was determined to be 9.0 x 10(-4) cm(2)/V s.

Homologation method for preparation of substituted pentacenes and naphthacenes.

Multi-substituted pentacenes, such as 1,2,3,4,6,8,9,10,11,13-decasubstituted pentacenes (Type I), 1,2,3,4,6,13-hexasubstituted pentacenes (Type II), 1,2,3,4-tetrasubstituted pentacenes (Type III), and 2,3-disubstituted pentacenes (Type IV), 1,2,3,4,6,11-hexasubstituted naphthacenes (Type V), 1,2,3,4-tetrasubstituted naphthacenes (Type VI), and 2,3-disubstituted naphthacenes (Type VII), were prepared by a homologation method. The homologation method involved the conversion of phthalic acid ester derivatives to two ring extended phthalic acid ester derivatives via diynes and metallacyclopentadienes using transition metals, such as Zr and Rh. For the formation of pentacenes of Type III and Type IV and naphthacenes of Type VII, trimethylsilyl-substituted diynes were used for zirconocene-mediated cyclization. Elimination of the trimethylsilyl groups after the cyclization afforded nonsubstituted position on pentacenes or naphthacenes. Structures of 1,4,6,8,9,10,11,13-octaethyl-2,3-bis(methoxycarbonyl)pentacene (9a) and 8,9,10,11-tetraethyl-2,3-bis(methoxycarbonyl)-1,4,6,13-tetrapropylpentacene (9b) were determined by X-ray analysis. The structure of 9a had the herringbone packing system in the crystal like nonsubstituted pentacene. However, 9b, whose substituents at 1,4,6,13-positions were changed from Et to Pr at 1,4,6,13-positions of 9a, had the face parallel plane system in the crystal.

Chromium-mediated synthesis of polycyclic aromatic compounds from halobiaryls.

[reaction: see text] Reaction of 2,2'-dihalobiphenyl with butyllithium followed by the addition of chromium(III) chloride and alkynes afforded the corresponding phenanthrene derivatives via formal [4 + 2] cycloaddition. A variety of alkynes could be used for this reaction, such as alkyl, aryl, silyl, and alkoxycarbonyl alkynes. Repetitive process of the reaction gave more extended polycyclic compounds such as benzo[g]chrysene and azacyclopentaphenalene derivatives.

Formation of linear tetramers of diarylalkynes by the Zr/Cr system.

The reaction of diarylalkynes with Cp2ZrBu2 and successive treatment with CrCl3 afforded linear tetramers of diarylalkynes, (1E,3E,5E,7E)-octatetraenes. On the other hand, dialkylalkynes did not give the corresponding octatetraenes but cyclized products, such as pyridines and pyridones, by the reaction with nitriles and isocyanates.

Pd-catalyzed reactions of o-diiodoarenes with alkynes for aromatic ring extension.

[reaction: see text] A new and efficient palladium-catalyzed reaction of o-diiodoarenes with internal alkynes produces naphthalenes or anthracenes in good to excellent yields. This procedure provides a simple, catalytic, and straightforward ring-extension method for constructing substituted polycyclic aromatic compounds.

Novel synthetic route to octasubstituted naphthalenes from four alkynes and one olefin unit via zirconacyclopentadienes and 1,2-diiodo-3,4,5,6-tetraalkylbenzene.

1,2,3,4-Tetrasubstituted benzene derivatives were prepared by the reaction of zirconacyclopentadienes with vinyl bromide in the presence of NiCl(2)(PPh(3))(2). 1,2-Diiodo-3,4,5,6-tetraalkylbenzenes were formed by treatment of 1,2,3,4-tetraalkylbenzenes with iodine and periodic acid in the presence of a catalytic amount of sulfuric acid. Reaction of the 1,2-diiodo-3,4,5,6-tetraalkylbenzenes with zirconacyclopentadienes in the presence of a stoichiometric amount of CuCl gave sterically crowded octasubstituted naphthalenes in moderate yields.

One-pot synthetic routes to multiply substituted indene derivatives by hydrolysis of zirconocene-mediated intermolecular coupling reactions of aromatic ketones and alkynes.

Two one-pot multicomponent synthetic methods for highly substituted indenes are described. The intermolecular coupling of aromatic ketones with alkynes on low-valent zirconocene species generates oxazirconacyclopentenes, which upon hydrolysis with 20% HCl for 3 h afforded indene derivatives in good to excellent yields. Similarly, the pair-selective coupling of two identical or different alkynes bearing at least one aromatic substituent formed zirconacyclopentadienes. Quenching of the reaction mixture with concentrated H(2)SO(4) also results in the formation of highly substituted indenes in high yields.