F-Butyllithium

West et al. have recently described the synthesis and reactions of a 1-germaallene. Germaallene 76 (Eq. (7)) is analogous to silaallene 59a and is synthesized by intermolecular addition of f-butyllithium to precursor 75, followed by salt elimination at —78 C. This germaallene is not stable above 0 C in solution, but remains intact until heated above 90°C in the solid state. In either case, the... 

Reaction of a-sulphinyl carboxylic esters 421 with carbonyl compounds has usually been performed using a Grignard reagent as a base. No condensation products are obtained using f-butyllithium or sodium hydride - (equation 251). The condensation products formed are convenient starting materials for the synthesis of a, ) -unsaturated esters and j -ketones . ... 

Jones179 pioneered in adding f-butyllithium to vinylhalosilanes as a route to several silenes of the general structure RR Si=CHCH2CMe3, as shown... 

Auner attributed their formation to dissociation of the siloxane to a zwitter-ionic species 95, followed by what appears to be a truly remarkable rearrangement. An alternative explanation for the formation of 94 involves the formation of the oxyanion 96 by the addition of f-butyllithium to the... 

Symmetric triblock copolymers P4VP-fr-PBd-fo-P4VP were prepared using a difunctional initiator derived from the reaction of m-diisopropenylbenzene with f-butyllithium at - 20 °C (Scheme 9) [27]. The synthesis was conducted in a mixture of toluene and THF at temperatures higher than room temperature for the polymerization of Bd, followed by a lowering of the temperature at - 78 °C and finally addition of an extra quantity of THF and 4VP. The 4VP content was kept lower than 30% to avoid problems arising from the poor sol-... 

Using alkyllithium compounds, a distannane with a very long Sn—Sn bond, 3.03A, and a syw-peripheral conformation122 was prepared. Thus, reaction of di-t-butyl(chloro)2,4,6-triisopropylphenyl)tin, 78, with f-butyllithium gives 1,1,2,2-tetra-f-butyl-l,2-(2,4,6-triisopropylphenyl)ditin, 79, which displays a restricted rotation about the Sn—C bond as well as the Sn—Sn bond, even at high temperatures. 

Reaction of GeBr4 with f-butyllithium gave a mixture of dibromo-di-t-butyl germane and l,l,2,2-tetrabromo-l,2-di-f-butyl-digermane, 114. 

Another application of the hydrazone method is the preparation of achy dr oxy carbonyl compounds (R4 = H in 37). The aldehydes/ketones 36 are first transformed into their corresponding SAMP-hydrazones 38, followed by deprotonation with f-butyllithium or LDA in THF. The resulting anion undergoes facile oxidation by treatment with 2-phenylsulfonyl-3-phenyloxaziridine (39), and the product can be obtained with good to excellent enantioselectivity (Scheme 2-23).39b... 

Polymerization in electrostatic systems like the ones mentioned above is stericaUy inhibited by alkyl substitution at the a-carbon which must assume a coordination number greater than 4. Coates and Glockhng have treated this inhibition of polymerization in terms of decreased electronegative character of the branched alkyl groups. Therefore, stimulated by the idea that f-afkylhthium compounds may exist as low polymers or even as monomeric molecules, Weiner and coworkers and Kottke and Stalke have isolated f-butyllithium as a pure substance for the first time and characterised it by spectroscopic methods and X-ray diffraction. The colourless crystalline solid was found to be tetrameric over a range of concentrations in both benzene and hexane ... 

In the Raman spectrum of f-butyllithium-7, only the strongly polarized band at 521 cm shifts significantly upon Li substitution (563 cm ) (Table 2). It was assigned to a totally symmetrical C—Li stretching mode. The peak at 525 cm in the IR spectrum was attributed to an impurity, because it exhibited widely variable intensity in various determinations and disappeared in one spectrum. ... 

It was already established that pure ethyl-" " and f-butyllithium exist as six- and fourfold polymers, respectively, in benzene solution. Apparently, C—Li bond cleavage takes place in this solvent leading to an exchange of alkyl groups between polymeric organo-lithium molecules when both compounds are present. The products are believed to be electron-deficient polymers of the type (EtLi) (f-BuLi) , wha-e m is a small number such as 4 or 6. ... 

The nucleophilic attack of f-butyllithium on lithium vinylidene carbenoids has also been used for synthetic purposes in as far as the reaction permits to generate sterically hindered alkenes. Thus, treatment of the dibromoalkene 78 generated from adamantanone with an excess of f-butyllithium results in the formation of the alkene 79 that contains three bulky substituents at the double bond (equation 43) . In an analogous way, a f-butyl residue is introduced into chloroenamine 80 (equation 44) . 

In the group of van Koten, dilithiated precursors for the peripheral functionalization of carbosilane dendrimers were generated by deprotonation of compounds 32, 34a and 34b using f-butyllithium. The reaction was effected in n-pentane at room temperature, using the appropriate amount of the alkyllithium base. Dilithiated compounds 33, 35a and 35b were almost quantitatively obtained, the para positions of the aromatic ring systems... 

Three different di- and trilithiated phenylmethanes 93, 95 and 97 were generated by Baran Jr. and Lagow. Dichlorodiphenyhnethane (92), dichlorophenyhnethane (94) and trichlorophenyhnethane (96) were reacted with the appropriate amount of f-butyllithium in THF at very low temperatures. Except for dihthiodiphenyhnethane (93), the observed yields were very low, verified by deuteriolysis of the lithiated compounds (Scheme 33). 

The dilithiated vinyllithium compound 1,2-dilithioethylene (132) was synthesized by Maercker and coworkers, using the mercury-lithium exchange reaction . Bis(chloromercurio)ethylene (131) was reacted with four equivalents of f-butyllithium... 

Two years later, the same group reported a formal synthesis of ellipticine (228) using 6-benzyl-6H-pyrido[4,3-f>]carbazole-5,ll-quinone (6-benzylellipticine quinone) (1241) as intermediate (716). The optimized conditions, reaction of 1.2 equivalents of 3-bromo-4-lithiopyridine (1238) with M-benzylindole-2,3-dicarboxylic anhydride (852) at —96°C, led regioselectively to the 2-acylindole-3-carboxylic acid 1233 in 42% yield. Compound 1233 was converted to the corresponding amide 1239 by treatment with oxalyl chloride, followed by diethylamine. The ketone 1239 was reduced to the corresponding alcohol 1240 by reaction with sodium borohydride. Reaction of the alcohol 1240 with f-butyllithium led to the desired 6-benzylellipticine quinone (1241), along with a debrominated alcohol 1242, in 40% and 19% yield, respectively. 6-Benzylellipticine quinone (1241) was transformed to 6-benzylellipticine (1243) in 38% yield by treatment with methyllithium, then hydroiodic acid, followed... 

The greater acidity of the a-protons of pyrroline compared to the pyrrolidine is demonstrated by the fact that whereas n-butyllithium is strong enough to form the unsaturated (sp2) carbanion, f-butyllithium is necessary for the saturated (jp3) system. 

Polymerization in aliphatic hydrocarbons is considerably slower than in aromatic hydrocarbons because of decreased dissociation of initiator and propagating ion-pair aggregates. The course of reaction in aliphatic hydrocarbons is complex compared to that in aromatic solvents. Initiation is very slow at the start of reaction hut proceeds with autoacceleration as cross- or mixed association of initiator and propagating ion pairs replaces self-association of initiator. Cross-association is weaker and results in an increased concentration of monomeric initiator. This effect may also explain the higher-order dependence of Rj on initiator (typically between and 1-order) in aliphatic solvents, especially for r- and f-butyllithium. Rp is still -order in initiator independent of solvent. 

In a modified procedure the free carboxylic acid is treated with a mixture of mercuric oxide and bromine in carbon tetrachloride the otherwise necessary purification of the silver salt is thereby avoided. This procedure has been used in the first synthesis of [l.l.l]propellane 10. Bicyclo[l.l.l]pentane-l,3-dicarboxylic acid 8 has been converted to the dibromide 9 by the modified Hunsdiecker reaction. Treatment of 9 with f-butyllithium then resulted in a debromination and formation of the central carbon-carbon bond thus generating the propellane 10." ... 

Direct lithiation of 2-/r t/-butyl-4(3//)-quinazolinone 76 with jr f-butyllithium and bis(dimethylamino)ethane (TMEDA) followed by quenching with diphenyldisulfide gave the 5-phenylthio derivative 77 in moderate yield, although a mixture of 5- and 8-substituted products was obtained on quenchinq with di-fetZ-butyldisulfide <2004T7983>. 

The most recent method for /3-lactone synthesis involves a very novel approach. Phenyl-ethynolate anion (which may be in equilibrium with phenylketene anion) can be generated by the reaction of n-butyllithium or f-butyllithium in THF at -78 °C. This highly nucleophilic species reacts with cyclohexanone to give the spiro-/3-lactone (54), probably through intermediacy of the lithium alkoxide of the /8-hydroxyketene (53). The /3-lactone (54) was isolated in about 50% yield (79LA219,82JA321). 

As shown in equation 53, when the zincated hydrazone, prepared from hydrazone by treatment with 2 equivalents of f-butyllithium and zinc(II) bromide, is treated with alkenylborane, the a-borylorganozinc is obtained with high diastereoselectivity. This pseudo-gem-dimetal species reacts with allyl halide stereospecifically. Through the transformation, three stereogenic centers are constructed diastereoselectively77. 

The trimethylsilyl radical produced either rapidly dimerizes or reacts with solvent so that very clean ESR spectra of the radical anion, with minimum interactions with the counterion, can be obtained (116). Further reduction to dianions is very slow, and exhaustive reduction to anion radicals minimizes problems associated with exchange between anion radicals and unreduced substrate (115). It now appears that the solvent HMPA greatly facilitates the one-electron reduction, not only for trimethylsilylsodium, but also for organolithium and magnesium reagents (110). It was found that 0.1F solutions of methyl-, n-butyl-, or f-butyllithium or benzylmagnesium chloride will quantitatively reduce biphenyl to its radical anion in less than 10 minutes (110). 

Enantioselectire alkylation of amides. Two laboratories12 have used (S)-prolinol as the chiral auxiliary for a synthesis of chiral amides. Alkylation of the enolate of the amide 1 (prepared with LDA or f-butyllithium) proceeds with pronounced... 

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