Tert-Butyllithium: Lithium,

Bromopene Propane, 2-bromo- (8) 1-Propene, 2-bromo- (9) (557-93-7) tert-Butyllithium Lithium, tert-butyl- (8) Lithium, (1,1-dimethylethy )- (19) (594-19-4)... 

However, reaction of 218 (E = P, R = R = H, R = r" = Me) with rerr-butyl-lithium most probably yields 221. The phospholyl loses its electrophilicity and the iron atom bears a considerable negative charge. Addition of rerr-butyllithium (one equivalent) followed by methyl iodide (one equivalent) does not give any isolable product but leads to recovery of the starting 218 only. In excess tert-butyllithium and methyliodide, 222 (R = r-Bu, R = Me) was isolated (81IC3252). 

H), followed by bromine-lithium exchange using 2 equivalents of tert-butyllithium to give the desired intermediate. This intermediate readily picked up carbon monoxide and work-up of the reaction mixture gave indigo (Fig. 17) (ref. 31). 

The addition of carbonyl compounds towards lithiated 1-siloxy-substituted allenes does not proceed in the manner described above for alkoxyallenes. Tius and co-work-ers found that treatment of 1-siloxy-substituted allene 67 with tert-butyllithium and subsequent addition of aldehydes or ketones led to the formation of ,/i-unsaturated acyl silanes 70 (Scheme 8.19) [66]. This simple and convenient method starts with the usual lithiation of allene 67 at C-l but is followed by a migration of the silyl group from oxygen to C-l, thus forming the lithium enolate 69, which finally adds to the carbonyl species. Transmetalation of the lithiated intermediate 69 to the corresponding zinc enolate provided better access to acylsilanes derived from enolizable aldehydes. For reactions of 69 with ketones, transmetalation to a magnesium species seems to afford optimal results. 

Although the preparation of the substituted allene ether substrates for the Nazarov reaction is not the topic of this chapter, it is necessary to mention a few aspects of their synthesis. Lithioallene 1 (Eq. 13.13) can be trapped with chlorotri-methylsilane to give 35 [6]. Exposure of 35 to sec- or tert-butyllithium leads to allenyl-lithium 36, which can be trapped with alkyl halides or other electrophiles to give 37. Desilylation of 37 leads to 38. This is somewhat laborious, but it leads to allene 38 uncontaminated by propargyl ether 39. Exposure of 39 to n-butyllithium, followed by quenching with acid, typically produces mixtures of 38 and 39 that are difficult to separate. Fortunately, one need not prepare allenes 38 in order to access the C6-sub-... 

How well an organolithium reagent fares as an exchange component depends on its basicity. Thus, tert-butyllithium outperforms iec-butyllithium, which in turn is superior to butyllithium. MethyUithium is the least reactive alkyllithium but still surpasses phenyl-lithium, at least at low concentrations, i.e. the order is ... 

This reagent was obtained either from Aldrich Chemical Company, Inc., or Lithium Corporation of America, Bessemer City, NC. A technical data sheet is available from the suppliers. Solutions of ca. 2 M were titrimetrically analyzed for active alkyllithium by the tosylhydrazone method. It is advisable to make certain that the organolithium reagent to be used was prepared in pentane solution. This evaluation can be easily accomplished by the gas chromatographic analysis of the organic layer obtained from the hydrolysis, under a nitrogen atmosphere, of the tert-butyllithium solution to be used. Isobutane and pentane should comprise essentially all of the... 

The second problem results from the fact that the azaenolates exist as aggregates or mixed aggregates in ethereal solvents. Cryoscopic measurements established that the azaenolate generated from 4,5-dihydro-4-methoxymethyl-2-methyl-5-phenyloxazole and butyllithium in tetrahydrofuran is a dimer18. When the metalation was performed with butyllithium or tert-butyl-lithium, an aging effect was observed. Thus, the enantiomeric excess on alkylation drops from 43% to 28% and 11 % when the azaenolates generated at — 78 °C were allowed to warm to... 

The present method offers a more efficient and convenient two step route to the parent a,B-unsaturated acylsilane derivative. The first step in the procedure involves the conversion of allyl alcohol to a 11 y 1 tnmethylsilyl ether, followed by metalation6 (in the same flask) with tert-butyllithium at -75°C. Protonation of the resulting mixture of interconverting lithium derivatives (2 and 3) with aqueous ammonium chloride solution furnishes (1-hydroxy-2-propenyl)tnmethylsilane (4), which is smoothly transformed to (1-oxo-2-propenyl)trimethylsilane by Swern oxidation.6 The acylsilane is obtained in 63-68% overall yield from allyl alcohol in this fashion. 

There is a certain analogy between the aromatic anions of cyclopentadienide (C5H5 ) and boratabenzene (C5H6B ). l-Methylbora-2,5-cyclohexadienehas a more acidic proton connected to the, sp3-hybridized ring carbon atom than cyclopentadi-ene, due to the same tendency of aromatic anion formation [252, 253]. The related 1-phenyl-1,4-dihydroborabenzene affords the lithium salt of 1-phenylborataben-zene on treatment with tert-butyllithium. Like metallic complexes such as ferrocene formed by cyclopentadiene, boratabenzene also forms such sandwich -complexes with iron and cobalt. The iron complex can be acetylated under Friedel-Crafts conditions. 

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