Bases Butyllithium-Potassium /-butoxide

Base Reactions. Both metal reagents (1) and (2) act as bases. The tricyclic ether (3) is readily deprotonated by the hindered base (1), but pentylsodium or butylpotassium proved superior in other cases. However, reagent (1) provides an alternative to the -butyllithium-potassium-butoxide system (eq 1). ... 

A broad scope is documented for the preparation of suspensions of 2-alkenylpotassium lithium toV-butoxide complexes from unsaturated hydrocarbons by means of butyllithium/ potassium /erf-butoxidc (Schlosser Lochmann base LICKOR reagents )38-45,432 456. Examples are given in Section D.1.3.3.3.3.2.1. 

A very important consideration to the chemistry of BTFs is the stability of the CF3 group toward acid or base. The CF3 group of BTF is stable to strongly basic conditions. For example (Scheme 5), BTF can be treated with butyllithium/ potassium f-butoxide in tetrahydrofuran to prepare a lithiated aromatic compound, which yields 2-trifluoromethyl benzoic acid (TFMBA) upon treatment with CO2 [10]. 

Poly(e-mercapto acids). In a series of papers, Overberger and Weise (17, 20, 21) reported the polymerization of e-thiocaprolactone (XXIV) and of some substituted analogs (see Table VI). XXIV could be polymerized in bulk or tetrahydrofuran solution, using bases such as butyllithium, potassium ferf-butoxide, or sodium as initiators. A1C13 as initiator gave a crosslinked product. Linear poly(e-thiocaprolactone) is crystalline and soluble in chlorinated hydrocarbons. 

The S n2 reaction product, p-aminoesters 372, produced from the reaction of allyl bromide 371 and arylamine by treatment with triethylamine, could be converted into substituted p-lactams in the presence of base. Conventional bases such as ethylmagnesium bromide, -butyllithium, potassium tert-butoxide, lithium hydroxide and potassium hydroxide used in such cyclizations failed to give p-lactam 373. However, Sn[N(TMS)2]2 as a base in the cyclization of p-aminoesters could successfully cyclize 372 to give p-lactam 373 (Scheme 4.120). Under optimized cyclization conditions, it was found that 1.5 equiv. of Sn[N(TMS)2]2 in toluene under reflux for 6 h achieved the best yield (up to 83%.)... 

Introduction. The -butyllithium/potassium tert-butoxide reagent (n-BuLi/t-BuOK LIC-KOR Schlosser base) consisting... 

The regioselectivity (a vs. y) is controlledby many factors, such as the nature of the heteroatom, the base, the substituents bonded to the heteroatom, the electrophile, the solvent, and the reaction conditions. It has been proposed, as a rule of thumb, that for a given counter ion, e.g., lithium, anion-destabilizing substituents (e.g., OR, NR2) favor the attack by alkyl halides and protons at the y-position, while carbonyl compounds undergo reaction preferentially at the a-position. The complementary regioselectivity is encountered when anion-stabilizing substituents (e.g., SR, BR2) are bonded to the allyl moiety. A list of n-butyllithium/potassium ferf-butoxide metalated heterosubstituted alkenes is shown in Table 3. 

The first investigations in the 1960s [11,12] established the base-induced isomerization of alkyne precursors as the most practical and general route for the synthesis of alkoxy-and aryloxyallenes. In the meantime, a number of monosubstituted allenes 8 bearing an achiral or a chiral group R is smoothly accessible by this efficient procedure (Scheme 8.5) [1, 2,13-19]. Beside the most commonly used base potassium tert-butoxide, other bases, e.g. n-butyllithium, are also applicable for this isomerization. Recently, the yields of alkyne-allene isomerizations could be significantly increased, in particular with aryloxy-substituted allenes, by using microwave irradiation (Eq. 8.1) [20]. 

When treated with a strong base such as butyllithium or potassium tert-butoxide, 2-isocyano-tV[(S)-l-phenylethyl]propanamide (1) forms an enolate 2 which is not alkylated at low temperatures. Instead it rearranges on warming and cyclizes to give the enolate of 3,5-dihydro-5-methyl-3-[(,3 )-1-phenylctbylJ-4//-imidazol-4-onc (3) which can be alkylated with benzylic halides with excellent diastereoselectivities4,13. 3-Halopropenes or haloalkanes give much lower diastereoselectivities. 

A study investigated the use of various bases, such as potassium hydroxide, potassium tert-butoxide, sodium methoxide, methyllithium, rrrf-butyllithium, sec-butyllithium, phenyllithium, lithium diisopropylamide, and lithium hcxamethyldisila/anidc over a temperature range of — 78 to 80°C in the dehydrofluorination of 2-(fluoromethoxy)-l,l,l,3,3,3-hexafluoropropane to give 2-(fluoromethoxy)pentafluoropropene.28... 

Shibasaki made several improvements in the asymmetric Michael addition reaction using the previously developed BINOL-based (R)-ALB, (R)-6, and (R)-LPB, (R)-7 [1]. The former is prepared from (R)-BINOL, diisobutylaluminum hydride, and butyllithium, while the latter is from (R)-BINOL, La(Oz -Pr)3, and potassium f-butoxide. Only 0.1 mol % of (R)-6 and 0.09 mol % of potassium f-butoxide were needed to catalyze the addition of dimethyl malonate to 2-cy-clohexenone on a kilogram scale in >99% ee, when 4-A molecular sieves were added [15,16]. (R)-6 in the presence of sodium f-butoxide catalyzes the asymmetric 1,4-addition of the Horner-Wadsworth-Emmons reagent [17]. (R)-7 catalyzes the addition of nitromethane to chalcone [18]. Feringa prepared another aluminum complex from BINOL and lithium aluminum hydride and used this in the addition of nitroacetate to methyl vinyl ketone [19]. Later, Shibasaki developed a linked lanthanum reagent (R,R)-8 for the same asymmetric addition, in which two BINOLs were connected at the 3-positions with a 2-oxapropylene... 

While norbornene, norbornadiene, 2-triallkylsilylnorbornadiene, and 1,3,5-cycloheptatriene are selectively deprotonated by the LIC-NAOR mixture (butyllithium/sodium /f 7-butoxide), other less acidic substrates such as bicyclo[2.2.2]oct-2-ene, camphene, 3,3-dimethyl-l-butene, and tro/o-dicyclopentadiene require the use of stronger bases constituted by mixtures of pentylsodium/disodium pinacolate (NAC-NAOR) or pentylsodium/ potassium ftrt-butoxide (NAC-KOR). 

In the case of HWE reactions of phosphonate esters containing a charge-stabilizing electron-withdrawing group, for example, as in trimethyl phosphono-acetate, the carbanion is often generated by reaction with potassium fcrf-butoxide, sodium hydride, n-butyllithium or similar base. Direct reaction with an aldehyde or ketone then gives the ( )-a,P-unsaturated ester as the major product (see Protocol 6). The nature of the phosphonate (see Section 3), and the substitution of the aldehyde or ketone, can influence the stereochemical outcome of these reactions as can, to a lesser extent, the reaction temperature and solvent.16... 

This procedure consists of the synthesis of a precursor, methoxymethyl vinyl ether, an a-hydroxy enol ether, and the intramolecular hydrosilylatlon of the latter followed by oxidative cleavage of the silicon-carbon bonds. The first step, methoxymethylation of 2-bromoethanol, is based on Fujita s method.7 The second and third steps are modifications of results reported by McDougal and his co-workers. Dehydrobromination of 2-bromoethyl methoxymethyl ether to methoxymethyl vinyl ether was achieved most efficiently with potassium hydroxide pellets -9 rather than with potassium tert-butoxide as originally reported for dehydrobromination of the tetrahydropyranyl analog.10 Potassium tert-butoxide was effective for the dehydrobromination, but formed an adduct of tert-butyl alcohol with the vinyl ether as a by-product in substantial amounts. Methoxymethyl vinyl ether is lithiated efficiently with sec-butyllithium in THF and, somewhat less efficiently, with n-butyllithium in tetrahydrofuran. Since lithiation of simple vinyl ethers such as ethyl vinyl ether requires tert-butyllithium,11 metalation may be assisted by the methoxymethoxy group in the present case. 

Reactions of the Lochmann base (a mixture of butyllithium with potassium re/T.-butoxide in pentane [195]), with conjugated polyenes yield fully delocalized carbanions in high yield at a high rate [196]... 

Such deprotonations may be achieved with SchEosser s super base , a combinatian of butyllithium wid potassium terf-butoxide. Me,COK (Bu OK). This reagent is even more basic than organolithium species. 

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. 

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. 

The base-induced monodehydrochlorination reaction was originally introduced as the second step of a convenient two-step synthesis of methylenecyclopropanes from alkenes. The first step involves carbene-type cyclopropanation of the alkene with a 1,1-dichloroalkane and either butyllithium or sodium bishexamethyldisilazanide as the base. The dehydrochlorination is then carried out by reacting the intermediate 1-alkyl-1-chlorocyclopropane with potassium tert-butoxide in dimethyl sulfoxide. For ordinary unhindered chlorocyclopropanes this procedure gives from about 60% to nearly quantitative yields of products (Table 1). The ready availability of the starting materials and reagents makes the base-induced dehydrochlorination a most useful 1,2-elimination reaction for preparation of methylenecyclopropanes. The procedure is illustrated by the synthesis of l,l-dimethyl-2-methylenecyclopropane (3) from 2-methylpropene ( ) ... 

Treatment of the phosphine resin 33 with alkyl bromides, e.g. 34, gave the corresponding phosphonium bromide 35 in excellent yields. The formation of the phosphorane was described as a cmdal step, for which the transport of the base to the phosphonium site within the polymer was essential. Various bases, such as sodium hydride, potassium tert-butoxide in THF, and n-butyllithium in dioxane, have been employed. Good results for the formation of the ylide were obtained with a mixture of sodium methoxide, methanol, and THF, and more recently with sodium bis(trimethyl)silylamide in THF [34, 35]. After the addition of aldehyde 36... 

Phosphorus ylids are prepared by treatment of phosphonium salts with bases such as phenyllithium, butyllithium. dimsyl anion, or potassium f-butoxide. They are not isolated but used directly after preparation because they are sensitive to oxygen and moisture. The requisite phosphonium salts are available in great variety from the reaction of triphenylphosphine and primary or secondary alkyl halides, usually bromides [24]. 

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