Cyclopentadienide methyl

Di(l-azulenyl)(6-azulenyl)methyl cation (24+) represented in Figure 17 exemplifies the cyanine-cyanine hybrid (20). Di(l-azulenyl)methylium unit in 24+ acts as a cyanine terminal group. The tropylium substructure stabilizes the cationic state (24+). Reduction of 24+ should afford the neutral radical 24, which is stabilized by capto-dative substitution effect, because 24 is substituted with azulenes in the donor and acceptor positions. The anionic state (24") is also stabilized by contribution of the cyclopentadienide substructure, which should exhibit the third color change in this system. 

Methyl-3-buten-1 -ynyltriethyHead, 3413 Methylcopper, 0440 Methylenedilithium, 0401 Methylenemagnesium, 0402 Methyllithium, 0452 Methylpotassium, 0448 Methylsilver, 0421 Methylsodium, 0463 Octylsodium, 3053 Pentamethyltantalum, 2046 Potassium cyclopentadienide, 1846 Propylcopper(I), 1251 Propyllithium, 1253 Propylsodium, 1269... 

Calculations using GIAO and IGAIM methods have enabled the chemical shifts of methyl cation and anion to be determined by gauging the shielding of the nucleus by neighbouring electrons the experimental data for cyclopentadienide ion, benzene, tropylium ion, and cyclooctatetraene dianion have also been reproduced and the data have been correlated by a simple model that also accounts for the large downfield shifts found for carbenes.14... 

The resonance structures for the cyclopentadienide anions formed by loss of a proton from l-methyl-l,3-cyclopentadiene and 5-methyl-l,3-cyclopentadiene are equivalent. 

In order to avoid the presence of stereoisomers, a further pathway including a carbolithiation reaction delivering achiral titanocene dichlorides was explored. Different aryl or heteroaryl lithium species were reacted with 6-bis-/V,/V-di methyl -amino fulvene and therefore, the intermediate lithium cyclopentadienide and the resulting 6-bis-/V./V-dimethylamino-functionalised titanocene dichlorides become achiral. 

D-Mannitol was also used as a precursor for trehazolamine via its conversion into the (/ )-(—)-epichlorohydrin (162),91,92 which gave the optically active l-(hydroxy-methyl)spiro[2,4]cyclohepta-4,6-diene (163) in 60% yield upon treatment with lithium cyclopentadienide (Scheme 21).49 Conversion of 163 into the corresponding trichloroacetimidate 164,93 followed by reaction with I(,yy/w-collidine)2CI04, afforded... 

Enantioselective total syntheses of (-)-6-epitrehazolin and (+)-trehazolin were achieved by the synthesis of 275, which began with an asymmetric heterocycloaddition between [(benzyloxy)methyl]cyclopentadiene (263),108 prepared from thallous cyclopentadienide, and the acylnitroso compound arising from in situ oxidation of (,S )-mandelohydroxamic acid (264) with tetrabutylammonium periodate. Cycloaddition led to a mixture of 265 and its diastereomer (Scheme 35).109 The inseparable mixture was reduced to afford cyclopentenes 266 and 268 in 40% and 11 % overall yields, respectively, from thallous cyclopentadienide. Catalytic osmylation of 266 favored syn addition, while the osmylation of diacetate 267 was more selective and nearly quantitative, affording, after acetylation, compounds 270 and 269 in >5 1 ratio. 

Methyl lithium and butyl lithium are widely used for the synthesis of other organolithium compounds. For example, lithium cyclopentadienides are generally prepared by the reaction of the cyclopentadiene with butyl lithium. In contrast, the amido-alkali metal compounds are becoming increasingly important in the synthesis of organoalkali metal compounds with the heavier alkali metals. For example, l,2,4-tris(trimethylsilyl)-l,3-cyclopentadiene reacts with potassium bis(trimethylsilyl)amide to form potassium l,2,4-tris(trimethylsilyl)cyclopentadienide. ... 

Cp = Substituted or unsubstituted cyclopentadienide Cp = tj -CsMesi L = Ancillary ligand MMA = Methyl methacrylate Pn = Polymer chain. 

Exchange of cyclopentadienyl ligands by their substituted analogs has been reported by Nesmeyanov, Ustynyuk, and Rodionova. They have studied the reaction of nickelocene with lithium a-phenyl(dimethylamino-methyl)cyclopentadienide (225). 

A single-crystal X-ray structure determination revealed a constrained geometry of the bifunctional amide-cyclopentadienide ligand, that gives rise to the distortions in the metallocene geometry. The A-bonded methylene derived from a Cp methyl group is pulled out of the plane of the C5 ring toward the metal center by 0.52 A.123... 

The earbene produced from 5-methyl-5-chloromethylcyclopentadiene gives only 1-methylbenzvalene (33). This shows that the earbene adds to the 1- and 4-positions of the diene component. If the addition occurs at the 1- and 2-positions, the 2-methyl isomer should be formed. The reaction of lithium methylcyclopentadienide with methylene chloride and methyllithium affords 2- and 3-methylbenzvalene both of which are formed by the attack of methylene chloride or chlorocarbene at the unsubstituted carbon of the cyclopentadienide (34). 5-Methyl-5-cyclopentadienyl-carbene was shown by MINDO/3 calculation to have a bisected conformation which seems to be susceptible to 1,4-addition3S). 

Cleavage of a C —Cl and a C —O bond occurred on reaction of methyl tra i-3-(acetoxychlo-romethyl)-2,2-dimethylcyclopropanecarboxylate with sodium cyclopentadienide to give methyl tran.s-3-(cyclopenta-2,4-dienylidenemethyl)-2,2-dimethylcyclopropanecarboxylate. " Treatment of [cyclopropyl(phenylselanyl)methyl]triphenylphosphonium perchlorate with butyllithium followed by benzaldehyde resulted in cleavage of the C Se and the C-P bond and formation of a 1 1 mixture of ( /Z)-l-cyclopropyl-2-phenylethene in 76% yield.Re-... 

By the reaction with two equivalents of vinyllithium, triaminocyclopropenylium ions 12 were converted into the lithium cyclopentadienide derivatives 13, which could be doubly methylated by iodomethane or doubly protonated to give the cyclopentenylium ion salts 14. 

Reaction of (chloromethyl)diphenylphosphane (1) with sodium cyclopentadienide (NaCp) afforded [(diphenylphosphanyl)methyl]cyclopentadiene (2) in 50% yield after aqueous workup (Scheme 1). 2 is... 

A similar but chiral ligand system 110 was developed by Hidai by treatment of the known ferrocene 109 with hydrogen peroxide followed by methyl-ation with Mel and subsequent treatment of the ammonium salt with sodium cyclopentadienide and reduction of the phosphane oxide with LiAlH4 (Scheme 17). 

Ethylene—methyl acrylate (EMA) copolymers react with sodium cyclopentadienide yielding a polymer-bound Cp anion, which forms an EMA-bound metallocene when combined with CpZrCE or ZrCl4(THE)2 (Scheme 16). Both catalysts polymerize ethylene in isobutane or toluene slurries to polyethylene of relatively narrow molecular weight distribution MJ Mn = 2.3—3.0) when activated by MAO. 

In order to obtain [(trimethylsilyl)methyl]cyclopentadiene, a mixture of (chloromethyl)trimethylsilane (Aldrich) and sodium cyclopentadienide in anhydrous tetrahydrofuran (Aldrich) was stirred for two days at room temperature under a nitrogen atmosphere. The dark red Hquid obtained was filtered and distilled at room temperature (0.15 torr). The final product was employed during further kinetic studies. 

In a chiral approach to ferrocenyldiamines, various aryllithiums, in the presence of sparteine, and in toluene, were added to 6-dimethylaminofulvene, leading to chiral lithium cyclopentadienides. The latter can be transformed into fer-rocenes, via an Fe(II) salt. When the arylhthium is ortho-substituted by a methyl, and in the presence of a chiral binaphthyl alcoholate, instead of sparteine, the ratio of chiral to meso-ferrocene is 88/12 (in 94% yield) and the chiral one is almost pure (ee>99%) (Scheme 31) [52]. 

This salt appears to be stable indefinitely in air. It is unattacked by bromine, hydrogen bromide or hydrogen iodide, [34], but is nitrated by dinitrogen tetroxide or by nitric acid in acetic anhydride [35]. Other examples of substituted cyclopentadienide anions which can be handled in air include aroyl-, [20-22], fomyl-, [36], methoxycarbonyl-, [24,37-40], cyano-, [41-44], and methyl-sulphonyl-cyclopentadienides [45]. 

This salt forms colourless crystals which are stable in solution in tetrahydrofuran at room temperature. The dianion has 10 ir-electrons. Its H-n.m.r. spectrum [signals at S 4.98 (4H) and 5.72 (2H)] reflects the offsetting of the shift due to a diamagnetic current by an upfield shift due to the double negative charge. It react.s similarly to the cyclopentadienide ion with methyl lithium and dichloromethane to give a benzvalene derivative which explodes violently at temperatures as low as -40° [187] ... 

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