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Cyclopentane derivatives Q 0030Reaction of Zirconocene-Alkyne Complexes with Mo(CO) 6 . -Reaction of zirconocene-alkyne complexes, generated in situ from zirconocene-butene complex (I) and alkynes (II), with Mo(CO)6 affords regioselectively 2,3-disubstituted 5-ethylcyclopentenone derivatives (IV) via incorporation of one eliminated butene. -(MITO, S.; ZHOU, L.; XI, C.; TAKAHASHI*, T.; Chem. Lett. 35 (2006) 1, 122-123; Catal. Res.

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.

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.

in Wiley Online Library (wileyonlinelibrary.com).Metallacyclopentadiene, which is recognized as a metallo-heterocycle, is an important intermediate for the formation of aromatic derivatives. In this short review, we summarized the recent advance on construction of axial, central, planar, and helical chirality by transition-metal-catalyzed aromatic compounds formation via metallacyclopentadienes.

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.

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.

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