T-Butyl lithium

The initiation of polymerization of styrene and isoprene in benzene by t-butyl lithium reveals some complexities129) (e.g. zero order kinetics in monomer) not observed in the reaction proceeding in cyclohexane. Further studies of that system are needed. 

The first example of chemically induced multiplet polarization was observed on treatment of a solution of n-butyl bromide and n-butyl lithium in hexane with a little ether to initiate reaction by depolymerizing the organometallic compound (Ward and Lawler, 1967). Polarization (E/A) of the protons on carbon atoms 1 and 2 in the 1-butene produced was observed and taken as evidence of the correctness of an earlier suggestion (Bryce-Smith, 1956) that radical intermediates are involved in this elimination. Similar observations were made in the reaction of t-butyl lithium with n-butyl bromide when both 1-butene and isobutene were found to be polarized. The observations were particularly significant because multiplet polarization could not be explained by the electron-nuclear cross-relaxation theory of CIDNP then being advanced to explain net polarization (Lawler, 1967 Bargon and Fischer, 1967). 

Polarization is found in reactions involving chlorides. 1,1-Dichloro-2,2-dimethylcyclopropane (26) reacts with lithium ethyl in benzene-ether solution (40°) giving mainly l-chloro-2,2-dimethylcyclopropane (27 X = H) and 3-methyl-l,2-butadiene (28) both of which are polarized (Ward et al., 1968). If n- or t-butyl lithium are used in the reaction, the butene produced by disproportionation shows only net polarization. 

The zinc complex formed with V,V -diphenylformamidinate is structurally analogous to the basic zinc acetate structure, as [Zn4(/i4-0)L6], and the basic beryllium acetate structure. It is prepared by hydrolysis of zinc bis(diphenylformamidinate).184 Mixed metal zinc lithium species were assembled from dimethyl zinc, t-butyl lithium, V.iV -diphenylbenzamidine and molecular oxygen. The amidinate compounds formed are dependent on the solvent and conditions. Zn2Li2 and... 

In this method, Furstner converts N-BOC protected pyrrole to the 2,5-dibromo compound (122) with NBS and this is followed by metalation and carbomethoxylation with t-butyl lithium in THF and subsequent trapping of the metalated species with methyl chloroformate to yield a pyrrole diester (123). Bromination of this diester at positions 3 and 4 with bromine in water followed by Suzuki cross-coupling with 3,4,5-trimethoxyphenyl boronic acid yields the symmetrical tetrasubstituted pyrrole (125). Base-mediated N-alkylation of this pyrrole with 4-methoxyphenethyl bromide produces the key Boger diester (126) and thereby constitutes a relay synthesis of permethyl storniamide A (120). 

In solution lithium alkyls are extensively associated especially in non-polar solvents. Ethyllithium in benzene solution exists largely as a hexamer (9, 43) in the concentration range down to 0.1 molar and there is no evidence for a trend with concentration so presumably the hexamers persist to even lower concentrations. Indeed even in the gas phase at high dilution it exists as hexamer and tetramer in almost equal amounts (3). In a similar way n-butyllithium in benzene or cyclohexane is predominantly hexameric (62, 122). t-Butyl-lithium however is mostly tetrameric in benzene or hexane (115). In ether solution both lithium phenyl and lithium benzyl exist as dimers (122) and it has been suggested that butyllithium behaves similarly in ether (15) although this does not agree with earlier cryoscopic measurements (122). It is however certain that more strongly basic ethers cause extensive breakdown of the structure. 

To a solution of 0.60 g l-(4-bromo-2,5-dimethoxyphenyl)-2-(l-aza-2,5-disila-2,2,5,5-tetramethylcyclopentyl)propane in 10 mL anhydrous Et,0 under an inert atmosphere and cooled to -78 °C there was added 1.8 mL of a 1.7 M solution of t-butyl lithium in hexane. The resulting yellow solution was stirred for 20 min, and then treated with 1.65 mLof a 1.4M solution of ethylene oxide inEt,0, the stirring was continued for 40 min, then the reaction mixture allowed to come to room temperature over an additional 40 min. There was added 20 mL hexane, and the temperature increased to 50 °C for an additional 2 h. The reaction mixture was treated with 3 mL H,0 and diluted with 60 mL F.t,0. The organic phase was washed with saturated NH,C1, dried over anhydrous MgSQ4, and after filtering off the in-... 

Lewis acid-mediated addition of (phenylthio)trimethylsilane to acryloyl silane takes place to give l,3-bis(phenylthio)-l-trimethylsilylprop-l-ene (18). This compound may be deprotonated with t-butyl lithium at the /J-position and alkylated to give a range... 

Buchachenko (1974) has advanced another theory. He based his reasoning on the absence of the CIDNP signals for the reaction of //-butyl iodide with t-butyl lithium conducted in ether at -70°C. The halogen and metal quickly exchange under these conditions, but the C—C bond does not form. In contrast to the preceding scheme, Buchachenko s theory assumes that the radicals produced form complexes with the alkyl lithium associates. Alkyl... 

The tobacco alkaloid anabasine (37) has been synthesized from 3-pyridyl-lithium (prepared from 3-bromopyridine and t-butyl-lithium) by reaction with A piperideine at —120 °C.46... 

The product from Stepl (0.01 mol) was dissolved in 100ml THE, 17 ml 1.6 M methyl lithium (0.03 mol) added, cooled to —20°C, and 7 ml 1 M t-butyl lithium (0.01 mol) gradually added. Dimethyl formamide (0.02 mol) was added and the mixture stirred 1 hour. After slowly warming to ambient temperature the mixture was hydrolyzed with water, poured into diethyl ether, and concentrated. The material was purified by chromatography on silica gel with petroleum ether/EtOAc, 9 1, and the product isolated. 

A synthetically very powerful property of chromimn tricarbonyl arene complexes is the ability to stabilize a negative charge at both the a-and /3-positions of an alkyl side-chain. Deprotonation of the benzylic position using sodiiun hydride, t-butyl lithium, or potassium t-butoxide followed by addition of an electrophile affords alkylated products. The... 

However, when t-butyl lithium was used to generate an aryl lithium compound from an aryl bromide, the /-butyl bromide formed did not react with the lithium arenetellurolate . 

Carbodiitnides (332 Scheme 55) form amidines on treatment with NaBH4 in alcohols, Grignard reagents, sodium phenylacetylide, carbon monoxide in the presence of s-butyl- or t-butyl-lithium and nitrones catalyzed by HBF4. In the reaction of stannylated or silylated ynamines with carbodiimides... 

Treatment of (+)-(S )-4-t-butylphenyl(methyl)phenylphosphine with t-butyl-lithium results in the displacement of both phenyl and 4-t-butylphenyl anions with complete inversion of configuration at phosphorus in each case, indicating the absence of pseudorotation in the potential hypervalent anion intermediates (112). It has been suggested that these substitution reactions are best considered as classical... 

Metallation of the phosphole sulphides (167) with t-butyl-lithium, followed by treatment with an ester, gives the functionalized phosphole sulphides (168), which can be desulphurized by heating with, e.g., tri-n-butylphosphine to form the functionalized phospholes (169). ... 

The amide (39) affords a low yield of the 6-ary1-5-methyl phenanthridinium salt on treatment with t-butyl lithium (D. Hellwinkel, R. Lenz and F. Lammerzahl. Tetrahedron, 1983, 2073). Formanilides yield phenanthridines on treatment with phosphorus pentachloride (N.S. Narasimhan, toa, ait. )... 

Fig. 22. Structure of the hexameric/t-butyl lithium. The bonding involves Li-C as well as Li-H bonds...

Valerolactones. - Dianions (441), derived from the parent acrylic acids using t-butyl lithium, condense smoothly with epoxides in the presence of BF2-OEt2 to give generally excellent yields of the unsaturated lactones (442), useful as precursors to a wide range of valerolactones... 

Nucleophilic addition then occurs to give the vinylphosphonium salts (143), some of which are able to undergo a further addition of nucleophile. The French group has also discovered a new reaction of arylphosphonium salts with t-butyl-lithium, in which the t-butyl carbanion undergoes nucleophilic addition to an aryl group to form ylides, e.g., (144), which then undergo Wittig reactions... 

Substituted piperidines have been obtained from A -piperideine as shown in Scheme 43. An 85 15 mixture of the erythro- and threo-torms of the carbinol (111) is formed " in the synthesis of (rf/)-anabasine (110 R = 3-pyridyl), the use of t-butyl-lithium to form 3-Iithiopyridine from 3-bromopyridine is recommended." A -Piperideine is conveniently generated in solution by the action of potassium superoxide and a crown ether on an ethereal solution of N-chloropiperidine. 

Cyclic vinyl ether carbanions. Cyclic vinyl ethers can be metaiated by t-butyl-lithium at -78 to 5° if the concentration of THF is kept to a minimum (compare metaiation of methyl vinyl ether, 6, 372). The resulting carbanions react with alkyl iodides and carbonyl compounds to form adducts in about 50-75% yields. The products are useful for further transformations. ... 

Sulfoniumsalze RiR2RsS+X sind dagegen leicht zuganglich. Die Dar-stellung der entspr. Ylide erfordert aber niedrige Temperaturen (—70 bis —50° C) und starke, sterisch anspruchsvolle Basen wie t-Butyl-lithium oder Lithiumdiathylamid (17, 30, 42, 49),... 

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