T-BuLi

The derivative is stable to n-BuLi, t-BuLi (—78°), and pH 6-8. It is cleaved with NaOH, Me0H/H20 at reflux (96% yield). 

Dihydropyrans 88-90 are deprotonated at the vinylic position adjacent to oxygen by t-BuLi and the resulting anions add readily to alkyl halides, aldehydes, and ketones. Subsequent acid hydrolysis provides the products expected from reaction of an oj-functionalized pentanoyl anion 88 acts as HOCH2(CH2)3CO , 89 as 0CH(CH2)3C0 , and 90 as MeCO(CH2)3CO (77TL4187 81T3997). 

Limited examples of nontransannular C-H insertions occurring in metalated epoxides exist. Treatment of trons-di-tert-butylethylene oxide 56 with t-BuLi predominantly gave the diastereomeric alcohols 58 and 59 (Scheme 5.13) [27]. Mioskowski... 

Commonly employed anion-stabilizing groups are those containing silicon (Table 5.4, Entries 1-5). Magnus et al. reported that epoxysilane 147 could be deproto-nated with t-BuLi, and that the lithiated epoxide 148 thus generated could be trapped with allyl bromide to give epoxysilane 149 in a synthetically useful yield (Scheme 5.34) [55], Iodomethane (88%) and chlorotrimethylsilane (60%) could also be trapped. 

When n-BuLi is used instead of t-BuLi, the byproduct after desulfinylation (n-BuS(O)Ph) possesses an acidic proton, which is abstracted by the metalated epoxide. Hence, overall, a stereoselective protodesulfmylation is achieved. This can be used for the asymmetric synthesis of epoxides, such as that of (-)-disparlure from enantiopure sulfoxide 222 (Scheme 5.53) [78]. 

Hodgson very recently reported an efficient intramolecular and completely dia-stereoselective cyclopropanation of bisliomoallylic and trisliomoallylic epoxides based on the use of a-lithiated epoxides. In a seminal paper, Crandall and Lin had reported that the reaction between t-BuLi and l,2-epoxyhex-5-ene (100) gave, inter alia, small amounts oftrans-bicyclo[3.1.0]hexan-2-ol (102, 9%) (Eq. a, Scheme 8.28)... 

To a solution of TBDMSCHjC CSiMcj (2mmol, preparation given, but not detailed) in THF (6ml), cooled to -78°C, was added dropwise, with stirring, a solution of t-BuLi in pentane (2mmol, 1.8m). After 1 h at -78 °C, a freshly prepared solution of MgBrj (2.2 mmol, from Mg and... 

Notes, fa) Rate of metallation with t-BuLi varies from case to case. Lithiation of ally] alcohol trimethylsilyl ether proceeds to completion in 2 h at -78 °C, whereas the corresponding methallyl derivative requires 3.5 h at -33°C. 

To a stirred solution of (E)-l-bromo-l-hexene (10 mmol) in THF/EtjO/ pentane (24ml, 4 1 1), cooled to —120°C, was added t-BuLi (20mmol in pentane) over 20 min. The pale yellow solution was stirred for 2 h at —110 to... 

A commercial solution of f-BuLi in pentane may be substituted for t-BuLi in heptane. However, the lower volatility and higher flash-point of the heptane solvent makes t-BuLi in heptane much easier and safer to handle than this alternative. 

A broad synthetic approach to borinato complexes ( 6.5.3.3) via alkali-metal borinates has been developed. Treatment of 1-boracyclohexadiene with t-BuLi leads to the anionic borinato ligand ... 

---