Cyclopentadienide reactions with

Based on the above-mentioned stereochemistry of the allylation reactions, nucleophiles have been classified into Nu (overall retention group) and Nu (overall inversion group) by the following experiments with the cyclic exo- and ent/n-acetales 12 and 13[25], No Pd-catalyzed reaction takes place with the exo-allylic acetate 12, because attack of Pd(0) from the rear side to form Tr-allyl-palladium is sterically difficult. On the other hand, smooth 7r-allylpalladium complex formation should take place with the endo-sWyWc acetate 13. The Nu -type nucleophiles must attack the 7r-allylic ligand from the endo side 14, namely tram to the exo-oriented Pd, but this is difficult. On the other hand, the attack of the Nu -type nucleophiles is directed to the Pd. and subsequent reductive elimination affords the exo products 15. Thus the allylation reaction of 13 takes place with the Nu nucleophiles (PhZnCl, formate, indenide anion) and no reaction with Nu nucleophiles (malonate. secondary amines, LiP(S)Ph2, cyclopentadienide anion). 

TC-Cyclopentadienyl Nickel Complexes. Nickel bromide dimethoxyethane [29823-39-9] forms bis(cydopentadienyl)nickel [1271 -28-9] upon reaction with sodium cyclopentadienide (63). This complex, known as nickelocene, 7T-(C3H3)2Ni, is an emerald-green crystalline sandwich compound, mp 173°C, density 1.47 g/cm. It is paramagnetic and slowly oxidi2es in air. A number of derivatives of nickelocene are known, eg, methylnickelocene [1292-95-4], which is green and has mp 37°C, and bis( 7t-indenyl)nickel [52409-46-8], which is red, mp 150°C (87,88). 

Aryl-l,2-dithiolium salts are a source of either dithiatricyclodecadienes (29) or cyclopenta[fc]thiopyrans (30) depending on whether the initial ring opening resulting from reaction with a metal cyclopentadienide is followed by an intramolecular cycloaddition or a condensation <96LA109>. 

The preparation of U(CsH5)2Cl2 91) and U(C5Hs)Cl3 -DME 92) were reported shortly after thallium(I) cyclopentadienide was found to be useful in controlhng the stoichiometries of reactions with uranium and thorium tetrachloride 93, 94). 

A particularly useful reaction of this type involves the direct formation of hexakis(trifluoromethyl)cyclopentadiene (71) (Scheme 31), or the corresponding cyclopentadienide (72), from the diene (38) by a fluoride ion induced reaction with pentafluoropropene [67-69]. Recent work [54] has shown that very active sources of fluoride ion can be generated by direct reaction of amines, especially TDAE (43), with perfluorinated alkenes or perfluorinated aromatic compounds and these essentially solventless systems promote both oligomerisations (see above) and polyfluoroalkylations. The absence of solvent makes recovery of product very easy, e.g. in high-yielding formation of (73), (74) or (75) (Scheme 32). 

Within this review we describe a second reaction pathway, which includes a carbolithiation reaction and leads to achiral-substituted titanocene dichlorides also. Therefore, aryl lithium species are added to the identical substituted 6-aryl fulvenes. This leads to the formation of highly substituted, but achiral diarylmethyl-functionalised lithium cyclopentadienides as seen in Scheme 5, which can still be used in the transmetallation reaction with titanium tetrachloride. 

Reactions of the (Tj5-C5Hs)cobaIt-olefin complexes (26) prepared according to Eqs. (25) and (26) with alkali metals (Li, Na, K) in the presence of olefins lead to the elimination of the second C5H5 ligand from the cobalt (Scheme 5). Complexes 27a and 27b, or the mixed complex 27c are obtained in high yields [Eq. (28)]. The syntheses of the pure complexes 27a and 27b do not, of course, require the isolation of intermediates 26a and 26b. As mentioned previously, synthesis is readily achieved from cobaltocene (24) by reaction with either stoichiometric amounts or excess alkali metal in the presence of COD or ethylene [Eq. (24)]. The alkali metal cyclopentadienides which are formed are easily separated from the cobalt complexes and can be used for the synthesis of cobaltocene (51) [Scheme 5 Eq. (29)]. 

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... 

Cycloaddition of diazomethane to phospholes is a key step in the synthesis of the homophospholes (189). A simple route to phospholyl anions is offered by the reaction of the zircona-cyclopentadienide (190) with phosphorus trichloride, giving the intermediate chlorophosphole (191) which, on treatment with lithium metal, gives the related phospholyl derivative (192). ... 

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. 

The complexes 3 and 5 were transformed into the mixed sandwich complexes 6 by reaction with thallium cyclopentadienide in benzene and with sodium cyclopentadienide in ethanol, respectively. The structure was determined by X-ray crystallography. ... 

The reaction of trisubstituted cyclopropenylium salts 1 with hexacarbonylmolybdenum(O) or tetracarbonylmolybdenum(O) complex afforded the complex salt 15 or 16. The same reaction with 17, followed by treatment with thallium cyclopentadienide, yielded complex 18. - The structures of 16 (X = Br) and 18 (R = Ph, t-Bu) were determined by X-ray crystallography. 

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