Phenyllithium complexes

Wen and Grutzner used, among other NMR parameters, the QSC of the lithium enolate of acetaldehyde to deduce that it exists as tetramers of different solvation in THF and THF/n-hexane solvent systems . However, the most thorough study of Li QSC and the most interesting in the present context was reported by Jackman and coworkers in 1987167 -pjjg effects on the QSC values of both aggregation and solvation in a number of organolithium systems was studied in this paper, i.e. different arylamides, phenolates, enolates, substituted phenyllithium complexes and lithium phenylacetylide. 

With the aim to obtain additional benchmark values, a larger number of substituted phenyllithium complexes with known solid state structures were included in this study . They range from monomers of different solvation, over dimers and one trimer to different tetramers. The investigated aryl systems are shown in Scheme 2 and the obtained x values are reported in Table 7. 

Optimum Conditions for Preparing Benzyllithium from Toluene. Both the TMEDA and TED complexes of benzyllithium were investigated. Toluene metalation proceeds much faster than does benzene metalation under similar conditions. The benzyllithium complexes were more soluble in hydrocarbon solvents than were the corresponding phenyllithium complexes. This method of preparation of benzyllithium is the most convenient of the few literature procedures available. Other procedures described are the cleavage of benzyl methyl ether with lithium... 

Carbanions ia the form of phenyllithium, sodium naphthalene complex, sodium acetyHde, or aromatic Grignard reagents react with alkyl sulfates to give a C-alkyl product (30—33). Grignard reagents require two moles of dimethyl sulfate for complete reaction. 

Retention of configuration may be used for the synthesis of the intramolecular carbene complexes [87J0M(336)C1]. Methyl- or phenyllithium or di-... 

We examined the possibility of a direct formation of two C-C bonds by reaction of a carbanion with [Fe(arene)2]2+ in which the arene bears methyl groups. We could indeed repeat Hellings s experiments but found that mesitylene was the only aromatic allowing this possibility in reasonable yields. With p-xylene, a low yield of an unstable complex was obtained corresponding to double nucleophilic attack of phenyllithium on the same ring in spite of the bulk of the methyl groups [23]. Eq. (4) ... 

Nucleophilic acyl complexes can be 0-alkylated with hard electrophiles to yield the corresponding alkoxy- or (acyloxy)carbene complexes. The first carbene complex ever isolated [61] was prepared by this route the intermediate, anionic acyl complex was generated by addition of phenyllithium to tungsten hexacarbonyl (Figure 2.3). 

In the solid state NMR study, uncomplexed phenyllithium, assumed to be a tetramer, as well as the TMEDA complexed dimer and the PMDTA complexed monomer were investigated. Both Li and Li isotopes were used in the preparations. The C spectra of the complexes are presented in Figure 12. It is evident that the substitution of Li with Li has profound effects on the Unewidths, especially of the ipso-carbon at ca 180 ppm in the aggregated uncomplexed system (Figure 12a and 12b, respectively). This is in accordance with the previously mentioned study of methyllithium. However, even the other positions are affected by the dipolar couplings to the four quadrupolar lithium cations, but to a lesser extent due to the larger C-Li distances. 

Thiophene, 2-hydroxy-5-methyl-synthesis, 4, 926 Thiophene, iodo-Grignard reagents, 4, 79, 831 photolysis, 4, 832 reactions, 4, 932 with phenyllithium, 4, 831 synthesis, 4, 835, 934 Ullmann coupling reactions, 4, 837 Thiophene, 2-isopropyl-3-methyl-synthesis, 4, 901 Thiophene, mercapto-reactions, 4, 78 stability, 4, 825 synthesis, 4, 80, 835, 930-931 tautomerism, 4, 38, 727 Thiophene, 2-mercapto-5-methylthio-synthesis, 4, 872 Thiophene, 2-methoxy-chloromethylation, 4, 759 Thiophene, 3-methoxy-chloromethylation, 4, 759 Thiophene, 5-methoxy-2,4-dinitro-Meisenheimer complexes, 4, 815 Thiophene, 2-methoxy-5-methyl-Vilsmeier formylation, 4, 759-760 Thiophene, 2-methoxy-3-nitro-reactions, 4, 827 Thiophene, 2-methyl-bromination, 4, 799-800 conformation, 4, 32 HNMR, 4, 730 metallation, 4, 773 synthesis, 4, 885, 887 trifluoroacetylation, 4, 751 Thiophene, 3-methyl-bromination, 4, 799-800 conformation, 4, 32 H NMR, 4, 730 metallation, 4, 60 oxidation, 4, 800... 

More reactive anions such as the 2-lithio-l,3-dithiane derivatives, phenyllithium and r-butyllithium do not require a special solvent and proceed in high yield in THF. While HMPA is known to suppress the migratory insertion to CO in anionic complexes,127 it does not deter the CO insertion in these cases no example of direct alkylation is reported. The only electrophile which adds without CO insertion is the proton, as discussed above. Good alkylating agents (primary iodides and triflates, ally bromide, benzyl... 

Once complexed to palladium(II), the alkene is generally activated towards nucleophilic attack, with nucleophiles ranging from chloride to phenyllithium undergoing reaction. The reaction is, however, quite sensitive to conditions and displacement of the alkene by the nucleophile (path a) or oxidative destruction of the nucleophile can become an important competing reaction. Nucleophilic attack occurs predominately to exclusively at the more-substituted position of the alkene (the position best able to stabilize positive charge) and from the face opposite the metal (trans attack, path b) to produce a new carbon-nucleophile bond and a new carbon-metal bond. This newly formed a-alkylmetal complex (2) is... 

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