Lithium Compounds Butyllithium

The influence of 1,2-asymmctric induction on the exchange of diastereotopic bromine atoms has also been investigated22,23. Thus, treatment of the / -silyloxydibromo compound 15 with butyllithium at — 110°C in the presence of 2-methylpropana led to products 17-19 after the reaction mixture was warmed to 20 °C. The distribution of the products indicates that the diastereomeric lithium compounds 16 A and 16B were formed in a ratio of 84 16, with 16A being kinetically favored by 1,2-asymmetric induction. Formation of the m-configurated epoxide (cis,anti-18) was slowed to such an extent that its formation was incomplete and a substantial amount of the parent bromohydrin 17 remained. The analogous m.yyn-configurat-ed epoxide was not observed. Presumably for sterie reasons, the parent bromohydrin did not cyclize to the epoxide but instead led to the ketone 1923. 

Treatment of selenoacetals 24 with butyllithium at 78 °C leads to the chiral a-seleno lithium compounds 25. Selenoacetals are stable compounds and can be readily prepared by selenoacetal-ization of the corresponding aldehydes25,26. In contrast to the corresponding dithioacetals, no competing deprotonation occurs on treatment with butyllithium, even with selenoacetals derived from aromatic aldehydes. 

The action of t-butyllithium on 5-methylene-8-nonenyl iodide (206) leads to the lithium compound 207, which undergoes a tandem cyclization to yield eventually 84% of 2-methylspiro[4.4]nonane (208) (equation 102). An analogous reaction of the iodide 209 (equation 103) results in the [4.3.3]propellane 210 (81%) as a mixture of endo- and excMSomers1. ... 

A similar type of substitution, which clearly shows the electrophilic character, occurs in vinylidene carbenoids. In an early example of this reaction, Kobrich and AnsarP observed that the aUcene 70 results when the fi-configurated vinyl lithium compound 68 is treated with an excess of butyllithium and the fithioafkene 69 formed thereby is protonated (equation 41). Obviously, the nucleophilic attack of the butyl residue on the carbenoid takes place with inversion of the configuration. 

On the contrary the triphenylsilyl and triphenylgermyl group seem to have no acidifying effect. Lithiation in this case was neither possible with lithiumdicyclohexylamide plus HMPA nor with n-butyllithium or t-butyllithium plus HMPA. In this context it is noteworthy that bi trimethylsilyl)methane 42a) in contrast to bis(triphenylsilyl)methane reacts with n-butyllithium smoothly to the lithium compound The striking difference is well understandable if assuming in bis(tri-phenylsilyl)methane the resonance formulated in Scheme 52 because this brings a... 

Snyder51 has studied the 5-carbethoxy derivative of thieno[3,2-Z>]-pyrrole (460, R = H) and shown that the Mannich reaction gives 6-substituted products and acetylation takes place at C-2. Bromination gave a 2,6-dibromo-compound, and the N-benzyl-derivative (460, R = CH2Ph) yielded a 2-lithium-compound with butyllithium which was converted to a 2-carbomethoxy derivative.5,b... 

To a solution of bis(phenylthio)methane (2.324 g, 10 mmol) in THF (20 ml) stirred under nitrogen at 0°C, was added n-butyllithium (10mmol) within 7 min to afford a clear yellow solution of the lithium compound, which can be used for reaction after 10 min and which is stable at 0°C for at least 12h. 

Some information is available on other acrylates. N,N-disubstituted acrylamides form isotactic polymers with lithium alkyls in hydrocarbons (12). t-Butylacrylate forms crystallizable polymers with lithium-based catalysts in non-polar solvents (65) whereas the methyl, n-butyl, sec-butyl and isobutyl esters do not. Isopropylacrylate also gives isotactic polymer with lithium compounds in non-polar solvents (34). The inability of n-alkylacrylates to form crystallizable polymers may result from a requirement for a branched alkyl group for stereospecific polymerization. On the other hand lack of crystallizability cannot be taken as definite evidence of a lack of stereoregulating influence, as sometimes quite highly regular polymer fails to crystallize. The butyllithium-initiated polymers of methylmethacrylate for instance cannot be crystallized. The presence of a small amount of more random structure appears to inhibit the crystallization process1. 

Lithium Compounds Benzyllithium, 56 t-Butyl lithiopropionate, 252 Butyllithium, 56, 94, 150, 157, 165,... 

Octamethylcyclotetrasilazane (130) reacts with M-butyllithium or alkaline metals to give the alkali salts, which crystallize as dimeric THF adducts (equation 40). In the dimers, two eight-membered rings are connected by a planar alkali metal-nitrogen four-membered ring. Lithium is tricoordinated, sodium tetracoordinated and potassium penta- and hex-acoordinated. The coordinatively bonded THF in the lithium compound (131) can be exchanged with the Lewis base TMEDA103. 

The bis-lactim ether 20a reacts with butyllithium (THF, —78 °Q regiospecifically in the alanine part of the molecule to give the lithium compound 22. This gives with... 

The bis-lactim ether 20b of cyclo(L-Val-Gly) reacts regiospecifically with butyllithium to afford the lithium compound 31. The addition products (32) are formed with alkyl halides in good chemical yields and — depending on R — with 65->95 % de16). They have the (3R)-configuration, as derived either from the H-nmr-spectrum of 32 (Table 4) or, indirectly, from the sign of rotation of the (R)-amino acid methyl ester (34) obtained by hydrolysis. 

The bis-lactim ether 21a of 44 and glycine reacts with butyllithium to the lithium compound 45 which affords with alkyl halides in good chemical yields the (3R> alkylation products 46 with 70-95 % de (Table 7) 19 25>. The de values were determined either from the nmr-spectrum of 46 or, indirectly, from ee of the (R)-amino acid esters (type 34) obtained from 46 by hydrolysis (2 equivalents 0.25 N HC1, r.t.). 

The high rate of diene polymerization initiated by lithium compounds and the availability of much data reported in the literature prompted us to undertake a more detailed investigation. Polymerization was carried out in dimethyl ether in the presence of butyllithium and butenyllithium, with polymerization conditions similar to those used in the investigations of the NMR spectra of butenyllithium. 

A variety of tertiary benzylic lithium compounds have been prepared by addition of f-butyllithium in isooctane with TMEDA to substituted styrenes 34 at 243 K10 (equation 96). 

N-Alkyl-imidazoles and -benzimidazoles react with lithium or butyllithium at low temperatures to give the 2-lithio derivatives. It has been reported, though, that in the metalation of 1-methylimidazole a small amount of the 5-substituted compound is also... 

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