Bases t-BuOK

The diamide 62 is heated under reflux for several hours in t-butanol with the base t-BuOK as catalyst so it may be that the anion of the nucleophilic amine is involved. Afterwards, dilution with water and neutralisation to pH 7.5 with HC1 gives pure 63. 

An entirely different result is observed with Pic and 93d. Reaction of 93c with base (LDA, THF, —75 °C, 1 h t-BuOK, DMSO, 25 °C, 5 h) led to complete recovery of starting material. Pit/is also unreactive towards base (t-BuOK, DMSO, 70 °C, 6 h KAPA, 1,3-diaminopropane, 25 °C, 24 h). Thus, the impossibility of preparing a cyclopropyl anion of the type 94 from Pic and the extremely low acidity of 93d prevent a reaction with base although electron transfer from base to initiate pathway B (Scheme 6) could still occur. 

The finding that lithiation of la took place selectively at the aromatic ring rather than the benzyl position opened a way for the functionalization of la in a regioselective manner by means of metalation [58]. Thus la was treated with 3 equiv. of the Lochmann s base (t-BuOK, n-BuLi) in hexane and then the reaction was quenched with appropriate electrophiles, giving monosubstituted products lb, II, Ip, and Iq (Structures 2 and 22, Scheme 14) in good yields. When more excess base was employed, para-disubstitution products Ic, Im, and Ir... 

It doesn t work because it is not possible to have a strong acid (HsO ) and a strong base (t-BuOK) present in the same reaction flask at the same time (they would simply neutralize each other). In order to achieve the desired transformation, the OH group must first be converted to a tosylate (rather than simply being protonated), and then the desired reaction can be performed, as shown here ... 

Because of the increased acidity and reduced steric requirement of the carbohydrate hydroxyl, t-BuOK can be used as a base to achieve ether formation. 

Hydroxy group of rru -7,9u-H-7-(prepared from 7-formyl-2-(2-pyrimidyl)perhydropyrido[l,2-u]pyrazine by the treatment with MeOCH2P(Ph)3Cl in the presence of -Pr2NH in THF at 0°C, than with BuLi at room temperature (99MIP6). 

Potassium er -butoxidc was obtained from Sigma-Aldrich and used as received. Alternatively, equivalent results were obtained using t-BuOK that was prepared from potassium metal and anhydrous tert-butyl alcohol (t-BuOH) followed by removal of excess t-BuOH. In this case, the molecular weight of t-BuOK was calculated based on a 1 1 ratio of t-BuOK to t-BuOH (i.e., 186.34 for C8H1902K). 

Ordinary ketones are generally much more difficult to cleave than trihalo ketones or p-diketones, because the carbanion intermediates in these cases are more stable than simple carbanions. However, nonenolizable ketones can be cleaved by treatment with a 10 3 mixture of t-BuOK—H2O in an aprotic solvent such as ether, dimethyl sulfoxide, 1,2-dimethoxyethane (glyme), and so on, or with sohd t-BuOK in the absence of a solvent. When the reaction is applied to monosubstituted diaryl ketones, that aryl group preferentially cleaves that comes off as the more stable carbanion, except that aryl groups substituted in the ortho position are more readily cleaved than otherwise because of the steric effect (relief of stain). In certain cases, cyclic ketones can be cleaved by base treatment, even if they are enolizable. " OS VI, 625. See also OS VH, 297. 

In 2003, Sigman et al. reported the use of a chiral carbene ligand in conjunction with the chiral base (-)-sparteine in the palladium(II) catalyzed oxidative kinetic resolution of secondary alcohols [26]. The dimeric palladium complexes 51a-b used in this reaction were obtained in two steps from N,N -diaryl chiral imidazolinium salts derived from (S, S) or (R,R) diphenylethane diamine (Scheme 28). The carbenes were generated by deprotonation of the salts with t-BuOK in THF and reacted in situ with dimeric palladium al-lyl chloride. The intermediate NHC - Pd(allyl)Cl complexes 52 are air-stable and were isolated in 92-95% yield after silica gel chromatography. Two diaster corners in a ratio of approximately 2 1 are present in solution (CDCI3). 

In 2004, Bolm et al. reported the use of chiral iridium complexes with chelating phosphinyl-imidazolylidene ligands in asymmetric hydrogenation of functionalized and simple alkenes with up to 89% ee [17]. These complexes were synthesized from the planar chiral [2.2]paracyclophane-based imida-zolium salts 74a-c with an imidazolylidenyl and a diphenylphosphino substituent in pseudo ortho positions of the [2.2]paracyclophane (Scheme 48). Treatment of 74a-c with t-BuOLi or t-BuOK in THF and subsequent reaction of the in situ formed carbenes with [Ir(cod)Cl]2 followed by anion exchange with NaBARF afforded complexes (Rp)-75a-c in 54-91% yield. The chela-... 

Equations 37 and 38 show a convenient procedure for the preparation of acetylenes and polyenes which utilizes an excess of t-BuOK as a base in THE or THF-t-BuOH. 

An interesting example of trilithiation has been reported, wherein 3-(methylthio)thiophene 36 was exposed to the powerful base system LICKOR (t-BuOK/BuLi), giving direct access to the products 37 after quenching of the intermediate 38 with suitable electrophiles. Reactions involving 2-(methylthio)thiophene gave 2,5-disubstituted products resulting from a dilithiated intermediate <06S3855>. 

Notes 0 Potassium alkoxides (2.5 equiv) prepared in situ from the corresponding alcohols with KH in THF were allowed to reoctwith PhCHCI2 (1 equiv) and t-BuOK (equivalent to alkoxide) at 0°C for the period indicated. b Except entry 7, yields refer to the isolated one based on PhCHCI2. c Paladini, J. Chuche, J. Bull. Chim. Soc. Fr. 1974, 192. d Manat, P. Dieter, S. Angew. Chem. 1977, 89, 333. eMauz6, B. J. Organomet. Chem. 1979, 365, 1 70. f Tamura, Y. Bayomi, S.M. Sumoto, K. Ikeda, M. Synthesis 1977, 693. 

Notes ° Unless otherwise noted, sodium alkoxides (1.25-2.5 equiv) prepared in situ from the corresponding alcohols with NaH in THF were allowed to react with CICH2SPh (1 equiv) and t-BuOK (equivalent to alkoxides) for the period indicated. b All products showed satisfactory spectra I data (IR,1H NMR, and mass). c Yields refer to the isolated yield based on CICH2SPh. d Satisfactory analytical results were obtained for these compounds. ef-BuONa (2.5 equiv) was employed in place of t-BuOK. f [3.3-dimethyl-2-(phenylthio)cydopropyl]methanol (mixture of isomers). BCH2=C=CHOCH2SPh. 

Yamamoto et al. [130] reported an intramolecular hydrocarbonation of allenes 199 to five- and six-membered carbocyles 200. In the case of n= 2 with the catalyst in the presence of t-BuOK only 10% yields were obtained, and without the base 62% With both the three and the four carbon bridges only an exo-trig cyclization was observed. 

The rate of isomerization of 2-methylbicyclo[2.2. l]hepta-2,5-diene [165] to 5-methylenebicyclo[2.2.1]hept-2-ene [166] by t-BuOK in DMSO (30) was not affected by the presence of 18-crown-6 at low base concentrations (Maskor-nick, 1972). At high concentrations of t-BuOK (>0.1 M), the reaction is zero... 

The Wittig reaction is one of the most important reactions in organic chemistry for synthesizing alkenes with unambiguous positioning of the double bond. The process involves a reaction between a phosphonium ylide and an aldehyde or ketone 150). The reacting ylide is formed from a phosphonium salt in a solution of a base such as NaH, t-BuOK, or NaOH 151) (Scheme 19). 

For the generation of carbanions, carbenes, etc., sodium hydroxide can be used as a base. Thus use of dangerous, expensive, and inconvenient reagents (t-BuOK, NaNH2, or NaH) is eliminated. Thanks to this, the use of large quantities of meticulously dried organic solvents is also avoided. 

Isobe et al. [114] have revealed the novel synthesis of indolenine spiro-p-lactams 173 (Scheme 40) in Chartelline, which belongs to the family of marine natural products. The starting precursors 172 were submitted to cyclization by employing a variety of bases such as EtMgBr, n-BuLi, t-BuOK, LDA, KHMDS, NaHMDS, and LiHMDS in THF at different reaction temperatures. Out of all these bases, LiHMDS at -78°C was found to be the best which provided the exclusive formation of spiro-p-lactams 173 without /V-methylamide 174 as a side product. 

The deuterium KIE in the nitrile-forming elimination of 467 (equation 275), promoted by Et3N-MeCN, t-BuOK-t-BuOH-and t-BuOK-DMSO, has been found533 to be dependent on the base-solvent variation from t-Bu-OH to DMSO. 

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... 

High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The base system employs a [RuCl2(phosphane)2(l,2-diamine)] complex as precatalyst, isopropanol serving both as solvent and hydrogen donor and in the presence of base, typically t-BuOK. Use of chiral diphosphanes, particularly BINAP compounds, and/or chiral diamines... 

Base-catalyzed hydrogen isotope exchange in inactivated selenophenes occurs only in highly basic media. The relative rates of exchange of deuterium at the a-position in furan, thiophene, and selenophene in 0.4 M t-BuOK/DMSO... 

In a general procedure, 1,1 equivalent of base (Cl ONa, t-BuOk or t-AmONa) was added to a stirred suspension of 1 equivalent of dry phosphonium salt 1 in boiling toluene. After being stirred for 10 min, the solution was filtered and evaporated to dryness. The crude material was essentially the desired indole with triphenylphosphine oxide. The yields for the reaction in scheme 2 are for isolated pure products obtained by preparative... 

Thus it is found that the relative amounts of olefinic products which result from reactions of 2-bromobutane with MeOK/MeOH, EtOK/EtOH and t-BuOK/DMSO are insensitive to changes in the base concentration (Bartsch et al., 1973a). In contrast, for eliminations induced by t-BuOK/t-BuOH, both positional and geometrical orientations are base concentration dependent. As the concentration of t-BuOK increases, a relatively higher proportion of 1-butene is... 

The mixture t-BuLi/t-BuOK is known as BoMosser s base, and is one of die most powerful bases known. It will abstract protons from allylic or benzylic positions, and will even deprotonate benzene. 

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