Sec Butyllithium

To a solution of 1.30 g (5.5 mmol) of (-)-sparteine in 20 mL of pentane and 2.5 mL of cyclohexane are sequentially added dropwise between —78, C and -70 C 5.5 mmol of an approx. 1.5 M solution of sec-butyllithium in 2-methylbutane/cyclohexane and 5.0 mmol of the 2-alkenyl diisopropylcarbamate in 5 mL of pentane. After 10 min stirring, the flask is raised from the dry-ice/acetone bath and cautiously shaken to remove the precipitate from the glass wall of the flask. The temperature must not rise above — 50 CC. After chilling the flask again to —70 °C, shaking of the flask is repealed and stirring is continued below — 70 C overnight. 

Freparatively useful induced diastereoselectivities have been reported mainly for 1,1-di-substituted allyllithium derivatives which bear carbanion-stabilizing substituents. l-[Methyl-thio-l-(trimethylsilyl)-2-propenyl]lithium106 and the appropriate 1-phenylthio107 derivative, generated from the allylic sulfide with sec-butyllithium, in the reaction with tetrahydropyranyl-protected pregnolone, furnish a single diastereomer. 

The addition of a cyclic vinyl sulfoxide anion to aldehydes has been reported only once14. Interestingly, 2,3,4,5-tetrahydro-l//-thiepane S-oxide cannot be metalated by lithium diiso-propylamide in tetrahydrofuran at — 78 °C. At higher temperatures ( — 20° to 0°) a white polymeric precipitate is formed. This polymeric product is also formed when the sulfoxide is treated with butyllithium or. wr-butyllithium in tetrahydrofuran even at — 78 C. However, metalation can be accomplished with. sec-butyllithium using an excess of N,N,N, N -tetramcthylethylenediamine in tetrahydrofuran at —78 C. In this case, a pale yellow solution is formed immediately and upon addition of benzaldehydc instantaneous dccolorization occurs yielding a mixture of diastereomeric alcohols in 90% yield. 

In nonpolar solvents, in spite of many attempts31), the problem of preparing efficient bifunctional initiators has not been entirely solved. Association between metal-organic sites causes insolubility (or even instability) of many bifunctional initiators. Satisfactory results 32,33) have been obtained with the diadducts of sec-butyllithium and diisopropenylbenzene (DIB). These adducts are made at a temperature chosen... 

Continuing his studies on the metallation of tetrahydro-2-benzazepine formamidines, Meyers has now shown that the previously unsuccessful deprotonation of 1-alkyl derivatives can be achieved with sec-butyllithium at -40 °C <96H(42)475>. In this way 1,1-dialkylated derivatives are now accessible. The preparation of 3//-benzazepines by chemical oxidation of 2,5- and 2,3-dihydro-l/f-l-benzazepines has been reported <96T4423>. 3Af-Diazepines are also formed by rearrangement of the 5//-tautomers which had been previously reported to be the products of electrochemical oxidation of 2,5-dihydro-lAf-l-benzazepine <95T9611>. The synthesis and radical trapping activities of a number of benzazepine derived nitrones have been reported <96T6519, 96JBC3097>. 

Trimethylsilylepoxides can be prepared by an addition-cyclization process. Reaction of chloromethyltrimethylsilane with sec-butyllithium at very low temperature gives an a-chloro lithium reagent that leads to an epoxide on reaction with an aldehyde or ketone.291... 

Good stirring is important to the success of this reaction, in order to provide efficient heat transfer during the addition of lithium tetramethylpiperidide and sec-butyllithium. The 2-1/2 x 3/4 inch stirring bar used is available from Aldrich Chemical Company, Inc. 

Parts A and B of the procedure correspond to preparation of lithium tetramethylpiperidide, and its use in the in situ preparation and addition of dibromomethyllithium to the ester 1 producing tetrahedral intermediate 2. In Part C a mixture of lithium hexamethyldisilazide and lithium ethoxide is prepared for addition in Part D to the solution of 2. The silazide base serves to deprotonate the mono and dibromo ketones that are formed on initial warming of the reaction to -20°C, thus protecting them as the enolate anions 4 and 3. Addition of the sec-butyllithium in Part... 

Solutions of butyllithium in hexanes and sec-butyllithium in cyclohexane were purchased from the Aldrich Chemical Company, Inc. It Is recommended that only freshly opened bottles or extremely well protected solutions be used as the presence of lithium butoxide in partially decomposed bottles results in formation of the corresponding butyl ester as an undesired by-product. 

Use of butyllithium in place of sec-butyllithium at this point results in formation of some a-butylated ester by-product later upon warming, while use of sec-butyllithium in greater excess results in tormation of methyl ketone Id (X, Y = H) in the final product. 

Lithium ethoxide Ethyl alcohol, lithium salt (8) Ethanol, lithium salt (9) (2388-07-0) sec-Butyllithium Lithium, sec-butyl- (8) Lithium, (1-methylpropyl)- (9) (598-30-1) Acetyl chloride (8,9) (75-36-5)... 

The carbon-carbon bond formation is accomplished by the reaction of the silicon-stabilized carbanions with electrophiles. Magnus and Roy have reported that methoxy(trimethylsilyl)methane is deprotonated with sec-butyllithium in... 

Fries rearrangement.1 Rearrangement of phenyl esters with Lewis acids results in a mixture of ortho- and para-phenolic ketones. In contrast, reaction of an o-bromophenyl ester with sec-butyllithium results in exclusive formation of the orf/jo-phenolic ketone by an intramolecular acyl rearrangement.2... 

Hydroxymethylation.1 Trimethylsilylmethanol is converted by reaction with butyllithium and C02 and then with sec-butyllithium into the lithiated lithium... 

The synthesis and characterization of a series of dendrigraft polymers based on polybutadiene segments was reported by Hempenius et al. [15], The synthesis begins with a linear-poly(butadiene) (PB) core obtained by the sec-butyllithium-initiated anionic polymerization of 1,3-butadiene in n-hexane, to give a microstructure containing approximately 6% 1,2-units (Scheme 3). The pendant vinyl moities are converted into electrophilic grafting sites by hydrosilylation with... 

A more recent application of this chemistry was reported by Oestreich and Hoppe [74] and involved the enantioselective deprotonation of the enyne carbamate ester 125 with sec-butyllithium in the presence of (-)-sparteine (Scheme 2.41). Removal of the pro-S hydrogen atom led to the corresponding organolithium intermediate, which then underwent a highly enantioselective intramolecular 1,4-addition to the enyne. Protonation of the resulting allenyllithium species 126 provided a 70 30 mixture of the two diastereomeric allenes 127. 

B. N,N-Diethyl-2-formyl-6-methoxybenzamide (3). An oven-dried, threenecked, 1-L flask equipped with a 100-mL pressure equalizing dropping funnel, nitrogen bubbler, internal low temperature thermometer pocket, and overhead stirrer is flamed under reduced pressure and allowed to cool under a stream of nitrogen. The flask is charged with 500 mL of THF (Note 6) and cooled to an internal temperature of -72°C. N,N,N, N -Tetramethylethylenediamine (TMEDA) (Note 8) (23.5 mL, 0.156 mol) followed by 128.7 mL (0.157 mmol) of 1.22 M sec-butyllithium in cyclohexane (Note 9) are then added. The internal temperature rises a little as the reagents are added. The fluorescent yellow solution is allowed to recool to an Internal temperature of -73°C. 

The Sparteine Method 42 was applied successfully to generate chiral a-lithiated pyrrolidine when using the Boc-protected (tcrt-butoxycarbonyl)pyrrolidine and sec-butyllithium/sparteine as an asymmetric deprotonating agent in diethyl ether at — 78 °C. Alkylation, silylation, stanny-lation and methylation occurred with good yield (70-75%) and high selectivity (95% ee)53. 

S,)-4,5-Dihydro-4-isopropyl-2-piperidinooxazole (1), easily available from chiral (5)-2-ethoxy-4,5-dihydro-4-isopropyloxazole and piperidine, can be deprotonated quantitatively by sec-butyllithium/TMEDA in diethyl ether/THF to 2 as is evident from subsequent silylation in high yield to give 3 (R = TMS). Only one single diastereomer could be detected by capillary gas chromatography. The same result was found on alkylation of 2 with iodomethane as electrophile, but the yield of 3 (R = CH3) drops to 30% in this case59. 

Recently, enantiomerically enriched 3-phenylalkanoic acid derivatives were prepared directly from a racemic dilithiated species obtained by double deprotonation of the A -m ethyl carboxamide with 2-3 equivalents of sec-butyllithium in THF/tm-butyl methyl ether (1 1) at — 78 °C after complexation with sparteine. Silylation or alkylation proceeded with good yields (77-86%) and enantioselectivity (80-94% ee)38. 

---