Butyllithium - potassium t-butoxide

N-Bis(trimethylsilyl)acetamide, 34 Butyllithium, 56, 150, 157, 193, 322 sec-Butyllithium, 188 Butyllithium-Potassium t-butoxide, 56 Butyllithium-Sodium t-butoxide, 59 Butyllithium-Tetramethylethylene-diamine, 56, 57 t-Butylmagnesium bromide, 59 Butylpotassium-Tetramethylethylene-diamine, 59 Butylsodium, 59... 

For purposes of comparison it should be noted that very powerful metallating agents (e.g., butyllithium/TMEDA or butyllithium/potassium t-butoxide) are capable of abstracting two or even three protons from various alkylated dienes. Thus, various hexadienes and methyl pentadienes have been converted to dianionic species, while 2,4-dimethyl-l,4-pentadiene, 1,4-heptadiene, and 1,4-cycloheptadiene have all been converted to trianions84-86. ... 

When pyridine is heated to 165 °C in MeONa-MeOD, H-D exchange occurs at all positions via small concentrations of deprotonated species, at the relative rates a (3 7, 1 9.3 12. However, using the combination n-butyllithium/potassium t-butoxide, efficient formation of 2-pyridylpotassium or 4-pyridylpotassium has been achieved." Some pyridines have been selectively lithiated at C-2 via complexes with hexafluoroacetone " complexation removes the lone pair (cf. section 5.5.1) and additionally provides inductive and chelation effects to assist the regioselective metallation. In practice, simple lithiopyridines are generally prepared by metal-halogen exchange, however the presence of chlorine or fluorine, or other substituents which direct ortho metallation, allows direct lithiation (section 5.5.1). 

However, when vinylic metalation is desired, competing allylic deprotonation may occur. In general, thermodynamic acidity and the kinetic preference for vinylic deprotonation of cyclic alkenes decrease with increasing ring size." The stable alkane-soluble reagent n-Butyllithium-Potassium t-Butoxide-TMEDA in hexane metalates Ethylene with potassium and effects selec-... 

Methyl-1,2,4-diazaphosphole (6) is metallated by butyllithium selectively in the 5-position <87JOM(3l9)49>. From the subsequent reaction with an electrophilic element halide, 5-methyl-, 5-stannyl-, and 5-boryldiazaphospholes (7) are obtained <87JOM(3l9)49,87TH 422-01 >. Catalytic amounts of potassium t-butoxide in acetonitrile-i/j effect an H/D-exchange, fast in the 5-position and slow in the 3-position of 1-phenyl-1,2,4-diazaphosphole <87JOM(3l9)49>. 

Chemical Co. Lithium t-butoxide and ji-butyllithium (15%) in hexane were purchased from Lithcoa Co. Sodium and potassium t-butoxides were purchased from MSA Research Corp. 

Bis(l, 5-cyclooctadiene)nickel(0), 35 t-Butyllithium, 58 Diacetatobis(triphenylphosphine)-palladium(II), 91 Menthol, 172 Mercury(II) chloride, 175 Palladium(II) acetate, 232 2-(Phenylseleno)acrylonitrile, 244 Potassium t-butoxide, 252 Tributyltin hydride, 316 Triphenyltin hydride, 335... 

Tetramethylethylenediamine, THE, sec-butyllithium, chlorodimethyloctylsilane THE, borane-tetrahydrofuran complex, hydrochloric acid CH2C12, vinyl chloroformate THE, potassium t-butoxide... 

Deprotonation of N-methylamines. Aliphatic N-methylamines are metallated exclusively on the methyl group by icc-butyllithium and potassium t-butoxide when excess amine is used as solvent. Deprotonation cannot be effected with -BuLi/KOC(CH,), or t-BuLi/KOC(CH3)j. The resulting carbanion reacts readily with alkyl halides, but gives... 

Isomerization of cis adducts of sulfenes with eneamines to trans adducts has been accomplished by treatment with n-butyllithium sodium methoxide or ethoxide, potassium t-butoxide, and triethylamine. " 7>-fl s-2,4-diphenyl-thietane 1,1-dioxide is converted to the cis isomer by treatment with sodium methoxide and equilibration of 2-methyl-4-phenylthietane 1,1-dioxide with bases gives mixtures containing 68-72% of the cis isomer. The results may be interpreted on the basis of a puckered ring and a preference for substituents to adopt a pseudoequatorial conformation. 

If the required reagent RLi cannot be obtained by lithiation of RH with, say, butyllith-ium, the metallation can sometimes be achieved by using a mixture of butyllithium and potassium t-butoxide (Schlosser s reagent or the LIKOR reagent) (e.g. equations 4-16 22 and 4-1713). The precise nature of the reagent is uncertain, but it is probably best represented as the organopotassium reagent, BuK. 

Dehydrobrommation. In a procedure for the preparation of tri-r-butylcyclo-propenyl fluoroborate (4), Ciabattoni et al. prepared dineopentylketone (1) by the Grignard synthesis formulated, converted it to the a,a -dibromide (2), and effected double dehydrobromination by treatment of this intermediate with potassium t-butoxide. The resulting cyclopropenone (3) was then brought into reaction with a solution of commercial t-butyllithium in pentane. The mixture was quenched with water, and the pentane layer was washed, dried, and evaporated on a rotary evaporator. The resulting pale-yellow oil is taken up in ether and treated at 0° under rapid magnetic... 

Wrrno reaction, bases n-Butyllithium (see Potassium t-butoxide). Lithium ethoxide. Potassium t-butoxide. Sodium bistrimethylsilylamide. Sodium ethoxide (see Potassium t-butoxide). Sodium bydride-Dimethyl sulfoxide [see DMSO-derived reagent (a)]. Sodium methoxide. 

Posner and Canella used the directed metalation technology for phenol C-alkylation (equation 35) phenol was dimetalated at both the hydroxy group and the < -position with t-butyllithium, and treatment with methyl iodide gave o-cresol . Brandsma and coworkers employed a complex reagent of butyllithium, Af,Af,A, A -tetramethylethylenediamine, and potassium t-butoxide for the metalation . Bates and Siahaan metalated cresols with butyl-lithium and potassium f-butoxide, and the o- and m-isomers gave the organometallic intermediate in good yield, while the yield was fair for the p-isomer . The Simmons-Smith... 

Lithiations are normally carried out with alkyllithiums or lithium amides, n-Butyllithium is the most widely used alkyllithium but t-butyllithium and occasionally i-butyllithium are used when more powerful reagents are required. Phenyllithium was used in older work but is uncommon now although it can be of value when a less reactive, more selective base is required. A very powerful metallating reagent is formed from a mixture of n-butyllithium and potassium t-butoxide this produces the potassium derivative of the heterocycle. 

Diarylalkynes The anion (1) of this diazo compound, prepared with n-butyllithium (or potassium t-butoxide) in THF at low temperatures, converts diaryl ketones into diarylalkynes in high yield (equation I). Heteroaromatic ketones behave in the same way, but only very electrophilic aryl aldehydes... 

Another recent asymmetric amino acid synthesis involves the reaction of a methyl 2-isocyanoalkanoate (5) with I in the presence of -butyllithium or potassium t-butoxide to form the metalated imidazolinones 6 in situ. Alkylation of 6 results in chiral 4,4-disubstituted imidazolinones (7) often in optical yields of 90-1007o. The highest optical yields are obtained when R has a higher priority than R. In this case 7 has the (R)-configuration. Reversal of the priority results in the (S)-configuration. Hydrolysis of 7 to the chiral amino acid 8 requires rather drastic conditions and is best conducted with base. This method was reported for the synthesis of twenty 2-imidazoline-5-ones of type 7. ... 

---