Butyllithium Subject

Reaction Mechanism. The reaction mechanism of the anionic-solution polymerization of styrene monomer using n-butyllithium initiator has been the subject of considerable experimental and theoretical investigation (1-8). The polymerization process occurs as the alkyllithium attacks monomeric styrene to initiate active species, which, in turn, grow by a stepwise propagation reaction. This polymerization reaction is characterized by the production of straight chain active polymer molecules ("living" polymer) without termination, branching, or transfer reactions. 

Although alkylidenecarbenes (R)2C=C and carbenoids 22-24 have an ip-hybridized carbene center similar to that of vinylidenecarbenes, the reactivity will be subject to the steric influence of substituents R3 and R4 because its location is closer to the carbene center than vinylidenecarbenes (Scheme 11). The steric effect was exerted in the reactions of 2-methylpropenylidene 22 generated from 2-methyl-1-chloropropene and butyllithium (BuLi) (Scheme ll).22 23 The results are summarized in Table 5. A more detailed discussion on the stereoselectivity of this reaction will be revisited in Section HI. A. 

Tetrahydro[l,5-tf]pyridine 52 was also subjected to lithiation by reaction with butyllithium and gave the 1-lithio derivative 56. This compound when treated with methyl iodide afforded the 4-methyl derivative 57. Further interesting transformations of 56 have also been carried out reaction with 1,3-dibromopropane gave first the... 

The formation and properties of octafluorodibenzothiophene (85) have been the subject of a series of papers by Chambers et al. Ullman coupling of bis(2-bromotetrafluorophenyl)sulfide gives 85 in quantitative yield [Eq. (6)]. An alternative route to 85 involves treating 2,2 -dihydrooctafluorobiphenyl with butyllithium and reacting the... 

The use of 4-bromo-3-formylthiophene (175) led to the third classical thieno[3,4-6]thiophene (8) via analogous reactions. The aldehyde (175) was protected by ketalization, and then subjected to bromine-metal exchange with n-butyllithium to give a lithio derivative which was reacted with sulfur, followed by methyl chloroacetate. The resulting ester-aldehyde derivative (176a) was condensed under the influence of base to give, after decarboxylation, thieno[3,4-6]thiophene (8 Scheme 61) <76AHC(19)123). 

The tacticity of anionically prepared polystyrenes has been the subject of extensive study by a number of groups of workers, mostly by means of 13C-NMR spectroscopy. From a study of the aromatic Cl resonances, Matsuzaki and coworkers found 234) that there is a tendency towards syndiotacticity when using -butyl-Iithium in toluene as initiator. From the sensitivity of the CMR spectrum to the nature of the solvent employed it was concluded that the polymerization did not conform to Bernoullian statistics. Randall examined the methylene resonances in the CMR spectrum and concluded that butyllithium initiated polystyrene is essentially atactic 235) and that propagation is Bernouillian. Uryu et al.236) examined polystyrene... 

The expedient and regioselective metalation of unprotected biphenyl-2-, -3-, and -4-carboxylic acids has been reported.59 Unprotected biphenyl-2-carboxylic acid has been cleanly metalated with. sex-butyllithium at the position adjacent to the carboxylate and can then be subjected to site-selective electrophilic substitution (Scheme 8). The remote C(2 )-position has been attacked by the superbasic mixture of n-BuLi and t-BuOK (LICKOR) in THF or benzene. The resulting dianion cyclizes to give the fluorenone skeleton. The mechanism of the metalation of homologous compounds, 2-(pyridin-3-yl)benzoic acid derivatives, with strong bases has also been discussed.60... 

A reaction vessel containing l,l,l,3,3,3-hexafluoro-2-propanol (168 g) and THF (1200 g) at —70°C was treated with 1290 ml of 1.6M of butyllithium, and the temperature was gradually increased to 0°C. The mixture was stirred at this temperature for 30 minutes and then treated with of 5-norbornene-2-carboxaldehyde (134 g) and stirred for an additional 60 minutes. After quenching with dilute hydrochloric acid, the mixture was subjected to standard aqueous workup. The crude product was purified by silica gel column chromatography, and the product was isolated in 80% yield. 

In the second step, aldehyde 50 is subjected to a Grignard reaction with isoprenyl Grignard reagent 53 which can be readily obtained from 2-bromopropene (51) via halogen-metal exchange using tert-butyllithium and subsequent transmetallation with magnesium bromide. 

After treating mc-2 with tert-butyllithium, both benzyllithium compounds (1-3)2 and m-3-TMEDA could be crystalhzed at -30 °C and subjected to X-ray structure analysis (Scheme 1). 

Epoxides were involved as intermediates when 1-cyclopropyl-1-[tris(methylsulfanyl)meth-yl]alkan-l-ols were subjected sequentially to butyllithium (1 equivalent) and CUCIO4 4MeCN (2 equivalents) and underwent rearrangement to thioesters with the carbonyl /i to the cyclopropane ring, e.g. formation of 7. A l-cyclopropyl-2-diazoalkanol reacted in a similar fashion on treatment with rhodium(II) acetate. ... 

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