Organolithium reagents Methyllithium

Several asymmetric 1,2-additions of various organolithium reagents (methyllithium, n-butyllithium, phenyllithium, lithioacetonitrile, lithium n-propylacetylide, and lithium (g) phenylacetylide) to aldehydes result in decent to excellent ee% (65-98%) when performed in the presence of a chiral lithium amido sulfide [e.g. (14)], 75 The chiral lithium amido sulfides invariably have exhibited higher levels of enantioselectivity compared to the structurally similar chiral lithium amido ethers and the chiral lithium amide without a chelating group. 

In order to prove the utility of this method and to ascertain the absolute configuration of the products, (S)-alanine has been enantioselectively prepared. The key step is the addition of methyllithium to the AjA -dimethyl hydrazone acetal 4c, derived from diol 3c. In accordance with 13C-NMR investigations it can therefore be assumed that all major diastereomers resulting from the addition of organolithium reagents to hydrazone acetals 4a-c derived from diols 3a, 3b or 3c (Table 3, entries 1 -6) have an S configuration at the newly formed stereogenic center. 

In some cases the yields were poor due to competing deprotonation of the substrate by the organolithium reagent. Deprotonation was the predominant reaction with methyllithium or when (Z)-2-(l-alkenyl)-4,5-dihydrooxazoles were employed. The stereochemical outcome has been rationalized as occurring from a chelated transition state. The starting chiral amino alcohol auxiliary can also be recovered without racemization for reuse. 

Whereas the reactions of sulfones with nucleophiles via pathways A and B of equation 1 are most frequently observed, the nucleophilic substitution reaction by pathway D has been observed only in the cases where the leaving carbanion can be stabilized, or in the highly strained molecules. Chou and Chang3 has found recently that an organolithium reagent attacks the sulfur atom of the strained four-membered sulfone in 34. When this sulfone is treated with 1 equivalent methyllithium, followed by workup with water or Mel, 38 or 39 are formed in high yield. 

The combination of equimolar amounts of tris(trimethylsilyl)methyllithium and zinc bromide in a THF/diethyl ether mixture, Scheme 27, furnished tris(trimethylsilyl)methylzinc bromide, as a lithium bromide/ether adduct.43 The compound, which may also be formulated as a lithium alkyldibromozincate, showed no ligand redistribution reactions. It is monomeric in solution and can be treated with 1 equiv. of an organolithium reagent to afford heteroleptic diorganozinc compounds. 

Early work has shown that the reaction of simple organolithium reagents with oxiranes lead mainly to products from a- or -deprotonation and not from the desired ring opening reaction. However, some reactions of methyllithium , aUyllithium , aryllithiums" , and vinyllithium/potassium reagents " with oxiranes are reported (Scheme 36). 

Trialkylated borazines R3B3N3H3 are deprotonated by organolithium reagents, but other reaction pathways also occur.For example, the reaction of Me3B3N3H3 with one equivalent of methyllithium produces the solvated monolithium derivative [(Me3B3N3H2)Li(OEt2)]2 (9.9), which is dimeric in the solid state. The formation of di- or trilithiated derivatives. 

Methyllithium-Methylaluminum bis(2,4,6-tri-t-butylphenoxide), 203 Organolithium reagents, 221 Trityllithium, 338 Boron reagents Alkyldimesitylboranes, 8 Bis(2,4-dimethyl-3-pentyl) tartrate, 36 Chlorodimethoxyborane, 73 Silicon reagents Titanium(IV) chloride, 304 Tin reagents... 

Dicarbonylcyclopentadienylcobalt, 96 Methyllithium, 188 Organolithium reagents, 209 Periodic acid, 238 Anthraquinones... 

Methyllithium-Methylaluminum bis-(2,4,6-tri-t-butylphenoxide), 203 Methylthiomethyllithium, 192 Nickel chloride-Lithium, 197 Organolithium reagents, 18, 56, 94,... 

Rli-rRNH2. Various organolithium reagents are converted into the corresponding primary amines by treatment with 2 equiv. each of methoxyamine and methyllithium in hexane-ether. Yields are in the range 55 95%. Omission of methyllithium or substitution by n-butyllithium markedly reduces the yield. In fact, use of methoxyamine alone for amination of organometallics was first reported in... 

Deprotonation of the hydroxyalkylpolysilanes la-lc with two or more equivalents methyllithium, rbutyllithium, or phenyllithium, respectively, leads to the trisilanes 6a-6e, which are formed by addition of the excess organolithium reagent to the polar Si=C-bond (Eq. 4). 

The products obtained from the reaction of (chloromethyl)trimethylsilane with organolithium reagents depend very much on the structure of the lithium compound. While lithium 2,2,6,6-tetramethylpiperidide initiates an a-elimination as described above, the treatment with sec-butyllithium leads to the formation of chloro(trimethylsilyl)methyllithium (11). This reagent cyclopropanates an electron-deficient alkene through sequential Michael addition and intramolecular ring closure (MIRC reaction), for example, the formation of cyclopropane 12. 

Organolithium reagents have the ability to cleave 1,1-dibromocyclopropanes reductively, giving rise to allenes (see also Section 5.2.2.1.1.4.). Thus, it was found that 1,1-dibromospiropentane (1) reacts with phenyllithium in diethyl ether to give ethenylidenecyclopropane (2). When the reaction was performed with methyllithium at 0°C, about 35% of the pure allene product could be isolated. ... 

Preparation by treatment of the /3-chloroethyl ester of formic acid with PC15.1 Preparation of cyclopropanols,2 When the ether is heated with methyllithium in ether solution a reactive carbenoid intermediate is formed and reacts with an olefin to form a 2-chloroethyl ether of a cyclopropanol (l).3 The product can be converted into the cyclopropanol itself in two ways either by splitting by an organolithium reagent (2a), or by dehydrochlorination followed by acid hydrolysis (2b) ... 

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