R Butyllithium

The first stable silaallene, 56, was synthesized in 1993 " " by the intramolecular attack of an organolithium reagent at the /f-carbon of a fluoroalkynylsilane (Scheme 16). Addition of two equivalents of r-butyllithium in toluene at O C to compound 54 gave intermediate 55. The a-lithiofluorosilane then eliminated lithium fluoride at room temperature to form the 1-silaallene 56, which was so sterically hindered that it did not react with ethanol even at reflux temperatures. 1-Silaallene 56 was the first, and so far the only, multiply bonded silicon species to be unreactive toward air and water. The X-ray crystal structure and NMR spectra of 56 is discussed in Sect. IVA. 

Intramolecular reactions are useful for forming small rings. The reaction of 1,3-, 1,4-, and 1,5-diiodides with r-butyllithium is an effective means of ring closure, but 1,6-diiodides give very little cyclization.84... 

Compounds containing two or more carbon-carbon double bonds also act as coupling agents and also as multifunctional initiators [Hadjichristidis et al., 2001 Quirk et al., 2000]. Such compounds can also be used to synthesize multifunctional initiators that subsequently produce star polymers. Consider l,3,5-tris(l-phenylethenyl)benzene (XL). Reaction with r-butyllithium produces a trifunctional initiator XLI, which initiates polymerization of a monomer such as styrene to form a 3-arm star polystyrene [Quirk and Tsai, 1998]. The 3-arm... 

There are few studies of the effect of temperature on monomer reactivity ratios [Morton, 1983]. For styrene-1,3-butadiene copolymerization by r-butyllithium in rc-hexane, there is negligible change in r values with temperature with r — 0.03, r2 = 13.3 at 0°C and n = 0.04, r% = 11.8 at 50°C. There is, however, a signihcant effect of temperature for copolymerization in tetrahydrofuran with r — 11.0, r2 = 0.04 at —78°C and r — 4.00, r2 = 0.30 at 25° C. The difference between copolymerization in polar and nonpolar solvents is attributed to preferential complexing of propagating centers and counterion by 1,3-butadiene as described previously. The change in r values in polar solvent is attributed to the same phenomenon. The extent of solvation decreases with increasing temperature, and this results in... 

A samarium(ll) species can also be obtained by reduction of samarium(m) bromide with lithium metal (Equation (27)) or samarium(lll) triflate with r r-butyllithium (Equation (28))4 Proportionation between 1 equiv. of samarium(O) and 2 equiv. of a samarium(m) species can also be employed for generation of a samarium(ll) species (Equations (29) and (30)). 

Indole synthesis. Fuhrer and Gschwend3 have converted N-pivaloylaniline into the dilithio derivative a by reaction with 2 equivalents of n-bulyllithium and have reported that orr/io-substituted derivatives are obtained in good yield by reaction of I Wilh an electrophile. The same species can be prepared somewhat more efficiently from iin o-bromo-N-pivaloylaniline (1) by bromine lithium exchange and N-deprotonation with methyllithium and r-butyllithium (equation I). This dilithium riegcnl can be used for synthesis of indoles.4 Thus it reacts with a bisclcctrophile... 

Litkiam trialkylborohydrides. The reaction of r-butyllithium with trialkyl-boranes provides a convenient route to lithium trialkylborohydrides.- ... 

Iodo-l-methyIindole yields l,l -dimethyl-2,2 -biindole with unactivated copper, whereas with an excess of activated copper, deiodination occurs, together with the formation of a triindolobenzene derivative (80T1439). An analogous reaction occurs upon the addition of copper(I) chloride to l-methyl-2-indolyllithium. It is apparent that only where the formation of the.-2-indolylcopper(I) derivatives is slow, as with deactivated copper on the iodoindole, does the Ullmann reaction between the indolylcopper(I) and the iodoindole occur. It is noteworthy that the 2,2 -biindole system is isolated from the sequential reaction of 1-benzenesulfonylindole with r-butyllithium and copper(I) chloride (80T1439). 

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 r-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 /3-hydroxyketene (53). The /3-lactone (54) was isolated in about 50% yield (79LA219,82JA321). 

Dehydrofluorination is used to obtain fluorinated acetylenes. Thermolysis of a dilute mixture of 1,1-difluoroethene (11) in argon has been studied in a single-pulse shock tube over the temperature range 1017-1427 C at low conversions, below 1107 C, the principal reaction is unimolccular elimination of hydrogen fluoride to yield fluoroacetylene (H).52 5- Elimination of hydrogen fluoride from 1,1-difluoroethene (11) by r-butyllithium also provides fluoroacetylene (12), in 90% yield.54... 

Methylmagnesium N-cyclohexyliso-propylamide, 189 By oxidation at an allylic carbon Selenium dioxide, 272 By reduction of a,0-unsaturated carbonyl compounds Sodium borohydride, 278 Sodium dithionite, 281 Other methods r-Butyllithium, 58 Butyllithium-Potassium f-butoxide,... 

More reactive anions such as the 2-lithio-l,3-dithiane derivatives, phenyllithium and r-butyllithium do not require a special solvent and proceed in high yield in THF. While HMPA is known to suppress the migratory insertion to CO in anionic complexes,127 it does not deter the CO insertion in these cases no example of direct alkylation is reported. The only electrophile which adds without CO insertion is the proton, as discussed above. Good alkylating agents (primary iodides and triflates, ally bromide, benzyl... 

This rearrangement can be used to effect the equivalent of the Amdt-F.istert synthesis4 by reaction of an ester with dibromomethyllithium (5, 403 6, 162-163) in the presence of a lithium dialkylamide and then with r-butyllithium (equation I). 

AIkylthio)allylritanium reagentS, RSCH=CHCH2TiL (l).9 The reagents are prepared by deprotonation of allylic alkyl (aryl) sulfides with sec- or r-butyllithium followed by addition of Ti(0-/-Pr)4 at - 78°. They can react with carbonyl compounds at the a- or "/-position. a-Adducts predominate in reactions with a- and /1-mono- and disubstituted sulfides, whereas /-adducts predominate in reaction with /-substituted sulfides. The a-adducts show high eryr/iro-selectivity. The products are useful precursors to alkenyl oxiranes and to 2-(arylthio)-l,3-butadienes. 

Subsequently, several nonkinetic approaches (32) were directed toward determining the structure of the live chain ends (e.g., H-NMR and 13C-NMR). For example, Bywater and co-workers (58) studied the addition of r-butyllithium to 1,3-butadiene and obtained a complex PMR spectrum for the addition product. They examined the effect of catalyst concentration on the microstructure of the polybutadiene and found that at high catalyst levels, the vinyl content increased as shown in Table II. 

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