Lithiation metallation

Methoxy-substituted aromatic compound 4 is lithiated metalation with Buli in THF, a step in which it proves useful to include lithium chloride. Because of the greater basicity of /t-butyllithium relative to 4. direct metallation is in fact possible thermodynamically, but /i-butyllithium is generally present in solution as a tetra-mer, and this reduces its reactivity. Addition of lithium chloride destroys these aggregates, and that eliminates the kinetic inhibition. Lithiated aromatic species 18 is further stabilized through chelate formation between lithium and the orr/icr-methoxy groups (ortho effect).8... 

M. Morita, O. Yamada, M. Ishikawa, J. Power Sources 1999, 81-82, 425-429. Charge and discharge performances of lithiated metal oxide cathodes in organic electrolyte solutions with different compositions. 

A battery element or elementary cell comprises two electrodes immersed in an electrolyte.4- 5 For instance, in a very common lithium-ion secondary battery, these two electrodes are made of a lithiated metal oxide and carbon. 

We speak of a direct conversion when there is an alteration of the chemical structure of the material in the wake of a reaction of decomposition of the original material, MX, in a composite electrode comprising nanoparticles of metal M° encapsulated in a LiX matrix. There is no formation of a lithiated metal alloy as before, but rather of metal particles which are inactive in comparison to lithium. The reaction leads to the formation of a metastable compound LiX (essentially Li20). In theory, this compound which is formed is not stable, but it is considered to be so because of its very slow rate of transformation. Many transition-metal oxides are involved oxides of cobalt CoO and C03O4, of copper CuO, of nickel NiO and of iron FeO and Fc203. Other compounds such as NiPs and FeS2 can also be considered. 

In addition to carbon, the attention has been focused on alloys and lithiated metal oxides as new materials for anodes in Li-ion cells. The reversible insertion of Li in metal/alloys has been studied for maity years because of their application in high-temperature molten salts Li cells. The electrochemical reactions that occur during discharge of a Li alloy electrode is ... 

The diffusion coefficients of lithium ion (Du+) in the three lithiated metal oxides are shown in Table 34.7. The diffusion steps play a significant role in the mechanistic aspects of the intercalation process. 

Positive electrode materials in commercially available Li-ion batteries utilize a lithiated metal oxide as the active material. The first Li-ion products marketed by Sony used LiCo02. Goodenough and Mizushima developed this material, as described in a series of patents." Recently, cells have been developed that utilize less costly materials, such as LiMu204 (spinel), or materials with higher coulombic capacity, such as LiNii Co 02. Commercial interest in LiNi02 has waned as its instability, driven by the energetic formation of NiO and oxygen, has been shown to contribute to safety issues."... 

Synthesis of Lithiated Metal Oxides. The synthesis of hthiated metal oxides, including LiCo02 and LiMn204, has be achieved through a wide variety of routes, although those practiced commercially use inexpensive starting materials, such as hthium carbonate, lithium hydroxide and the metal oxide. The physical and electrochemical properties of the materials may be controlled by the choice of starting materials and the preparation conditions. ... 

Note 1. The lithiation of monoalky1al 1 enes is not completely regiospecific. The ratio of a- to ylithiated allene varies from about 80 20 for methyl-allene to 93 7 for hexylallene. tert.-Butylallene, however, is metallated exclusively on the terminal carbon atom. 

Carbocyclic substitution can also be achieved by first introdueing a reactive organomelallic substituent. Preparation of organolithium reagents can be done by one of the conventional melhods. especially halogen-metal exchange or directed lithiation. Table 14.2 gives examples. 

In an extensive temperature study on the lithiation of 2-methylthiazole (157) J. Crousier reported (441) that three lithio salts are formed independently, and not through proton-metal equilibration, at low temperature (—78 C, as shown in Scheme 77). The 4-lithio derivative (160) is... 

Each of these intermediates can be hthiated in the 2-position in good yield. The reactivity toward hthiation is due to the inductive effect of the nitrogen atom and coordination by oxygen from the N-substituent. A wide variety of electrophiles can then carry out substitution at the 2-position. Lithiation at other positions on the ring can be achieved by halogen—metal exchange 3-hthio and 5-hthioindoles have also been used as reactive intermediates. 

Competitive metallation experiments with IV-methylpyrrole and thiophene and with IV-methylindole and benzo[6]thiophene indicate that the sulfur-containing heterocycles react more rapidly with H-butyllithium in ether. The comparative reactivity of thiophene and furan with butyllithium depends on the metallation conditions. In hexane, furan reacts more rapidly than thiophene but in ether, in the presence of tetramethylethylenediamine (TMEDA), the order of reactivity is reversed (77JCS(P1)887). Competitive metallation experiments have established that dibenzofuran is more easily lithiated than dibenzothiophene, which in turn is more easily lithiated than A-ethylcarbazole. These compounds lose the proton bound to carbon 4 in dibenzofuran and dibenzothiophene and the equivalent proton (bound to carbon 1) in the carbazole (64JOM(2)304). 

Directive effects on lithiation have also been studied. The regiospecific /3-metallation of A-methylpyrrole derivatives and 2-substituted furans has been effected by employing the directive effect of the oxazolino group (82JCs(Pl)1343). 2-Substituted furans and thiophenes are metallated in the 5-position. The formation of 2-lithio-3-bromofuran on treatment of... 

Methylthiophene is metallated in the 5-position whereas 3-methoxy-, 3-methylthio-, 3-carboxy- and 3-bromo-thiophenes are metallated in the 2-position (80TL5051). Lithiation of tricarbonyl(i7 -N-protected indole)chromium complexes occurs initially at C-2. If this position is trimethylsilylated, subsequent lithiation is at C-7 with minor amounts at C-4 (81CC1260). Tricarbonyl(Tj -l-triisopropylsilylindole)chromium(0) is selectively lithiated at C-4 by n-butyllithium-TMEDA. This offers an attractive intermediate for the preparation of 4-substituted indoles by reaction with electrophiles and deprotection by irradiation (82CC467). 

Neutral azoles are readily C-lithiated by K-butyllithium provided they do not contain a free NH group (Table 6). Derivatives with two heteroatoms in the 1,3-orientation undergo lithiation preferentially at the 2-position other compounds are lithiated at the 5-position. Attempted metallation of isoxazoles usually causes ring opening via proton loss at the 3-or 5-position (Section 4.02.2.1.7.5) however, if both of these positions are substituted, normal lithiation occurs at the 4-position (Scheme 21). 

Selenophene, 2,5-diamino-3,4-dicyano-synthesis, 4, 119, 964 Selenophene, 2,4-diaryl-synthesis, 4, 967 UV spectra, 4, 941 Selenophene, 2,5-diaryl-synthesis, 4, 967, 969 UV spectra, 4, 941 Selenophene, 2,5-dichloro-metallation, 4, 949 Selenophene, dihydro-3-methylene-synthesis, 4, 963 Selenophene, 2,5-dimethoxy-lithiation, 4, 949 Selenophene, 2,4-dimethyl-... 

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