Lithium f-butoxide

Mass spectra were also recorded for lithium f-butoxide and lithiomethyltrimethylsilane. It was demonstrated that lithium f-butoxide is a hexamer in the vapor phase, while lithiomethyltrimethylsilane has a nearly 100% tetrameric composition at 100 °C. Further on, the association of LiB(CH3)4 in the gas phase was examined by Stucky and coworkers, using They found that at an ionization potential of 18 eV and a temperature of... 

Lithium borohydride, 62 Lithium f-butoxide, 69 Lithium cyanohydridoborate, 92 Lithium diisopropylamide, 477 Lithium reductive deacetoxylation, 56 Lithium reduction of 17a-ethynyl-19-nortestosterone, 55... 

When treated with lithium f-butoxide in DMSO, selenophene79,84 exchanges a-deuterium atoms approximately 1.5 times faster than... 

The intramolecular Claisen condensation of the dimeric model (22, R = Me) of PMMA was observed during NMR analysis, even at low temperature. This condensation results in the formation of a cyclic /3-keto ester (23), methyl 2-lithioisobutyrate and lithium f-butoxide (equation 26). 

The selenium-stabilized carbanions derived by deprotonation of selenoacetals by strong bases, such as a mixture of KDA-lithium f-butoxide, LiTMP in HMPT/THF or LBDA in THE at -78 °C, react readily with a variety of electrophiles including primary or secondary halides, epoxides, ketones, aldehydes and enones, followed by deprotection, to give ketones, p-hydroxy ketones, a-hydroxy ketones and 1,4-dicar-bonyl compounds respectively. - ... 

DABCO). 1,5-Diazabicy do [5,4,0 ] undec-ene-5 (DBU). Diethylamine. Ethylene-diamine. Lithio propylidene-f-buty limine. Lithium bis(trimethylsilyl)amide. Lithium f-butoxide. Lithium diethylamide. Lithium diisopropylamide. Lithium N-isopro-pylcyclohexylamide. Lithium orthophosphate. Lithium 2,2,6,6-tetramethylpiper-ide. Lithium triethylcarboxide. 1,2,2,6,6-Pentamethylpiperidine. Piperazine. Potassium f-butoxide. Potassium hexamethyldi-silaznae. Potassium hydride. Potassium hydroxide. Pyridine. 4-Pyrrolidopyridine. Quinuclidine. Sodium ethoxide. Sodium methoxide. Sodium thioethoxide. Tetra-methylguanidine. Thallous ethoxide. Tri-ethylamine. 

ESTERIFICATION Boron trifluoride etherate. Diazomethane. Lithium f-butoxide. Triethyloxonium fluoroborate. Tris(2-hydroxypropyl)amine. 

Kuwajima and coworkers used very hindered bases such as (2) to deprotonate methyl alkyl ketones regioselectively in the presence of enolizahle aldehydes,21 One example of this amazing process is shown in equation (11) the reaction is reported to work equally well with other methyl ketones, including 2-pentanone. The process was also demonstrated with other bases in the reaction of 3-methyl-2-buta-none with dihydrocinnamaldehyde (equation 12). Among the bases that are effective are LDA, lithium hexamethyldisilazane, lithium f-butoxide and even lithium ethoxide. However, base (2) is superior, giving the aldol in 83% yield. 

Oxidation of alcohols. In a new method for oxidation of primary and secondary alcohols to aldehydes and ketones, respectively, the alcohol is converted into an alkoxymagnesium bromide by reaction with ethylmagnesium bromide in THF at 20° a solution of lithium f-butoxide (2.4 eq.) is added iiiul then, after 1 hr., NCS (2.4 eq.) is added. The suspension is stirred for 1 hr. 

The stereoregularity of polystyrenes prepared by anionic polymerization is predominantly syndiotactic (racemic diad fraction P = 0.53-0.74) and the stereoregularity is surprisingly independent of the nature of the cation, the solvent, and the temperature, in contrast to the sensitivity of diene stereochemistry to these variables [3, 156]. The homogeneous alkyllithium-initiated polymerization of styrene in hydrocarbon media produces polystyrene with an almost random (i.e., atactic) microstructure for example, was 0.53 for the butyllithium/toluene system [3, 191, 192]. A report on the effect of added alkali metal alkoxides showed that polystyrene stereochemistry can be varied from 64% syndiotactic triads with lithium f-butoxide to 58% isotactic triads with potassium f-butoxide [193]. 

When small amounts of water were deliberately added to butyllithium in hydrocarbon solutions, it was possible to prepare polystyrene with as much as 85% polymer that was insoluble in methyl ethyl ketone under reflux and identified as isotactic polystyrene by X-ray crystallography [194, 195]. Isotactic polystyrene (10-22% crystalline) can be prepared when lithium f-butoxide is... 

Anionic Oligomerization of chloral with lithium f-butoxide (5,6)... 

Anionic Cooligomerization of chloral and bromal with lithium f-butoxide or bomyl oxide followed by acetate end-capping (7)... 

Cationic copolymerization with excess trioxane always leads to a 1 1 copolymer. Even in anionic copolymerization of trioxane with excess isocyanates present, an alternating copolymer is always obtained, even though lithium f-butoxide polymerizes isocyanates to high-molecular-weight unipolymers. 

Diphenylmethylcarbanions. The carbanions based on diphenyl-methane (pZ a = 32) (see Table 1) are useful initiators for vinyl and heterocyclic monomers, especially alkyl methacrylates at low temperatures (46). 1,1-Diphenylalkyllithiums can also efficiently initiate the polymerization of styrene and diene monomers that form less stable carbanions. Diphenylmethyl-lithium can be prepared by the metalation reaction of diphenylmethane with butyllithium or by the addition of butyffithium to 1,1-diphenylethylene, as shown in equation 17. This reaction can also be utihzed to prepare ftinctionalized initiators by reacting butyffithium with a substituted 1,1-diphenylethylene derivative. Addition of lithium salts such as hthium chloride, lithium f-butoxide, or lithium 2-(2-methoxyethoxy)ethoxide with 1,1-diphenylmethylcarbanions and other organolithium initiators has been shown to narrow the molecular weight distribution and to improve the stabffity of active centers for anionic polymerization of both alkyl methacrylates and t-butyl acrylate (47,48). 

A dramatic development in the anionic polymerization of acrylate and methacrylate monomers was the discovery that by addition of lithium chloride it was possible to effect the controlled polymerization of f-butyl acrylate (86). Thus, using oligomeric (o -methylstyryl)lithium as initiator in THF at —78°C, the molecular weight distribution (M /Mn) of the polymer was 3.61 in the absence of lithium chloride but 1.2 in the presence of lithium chloride ([LiCl]/[RLi] = 5). In the presence of 10 equiv of LiCl, f-butyl acrylate was polymerized with 100% conversion and 95% initiator efficiency to provide a polymer with a quite narrow molecular weight distribution (My,/Mn = 1.05). More controlled anionic polymerizations of alkyl methacrylates are also obtained in the presence of lithium chloride. Other additives, which promote controlled pol5unerization of acylates and methacrylates, include lithium f-butoxide, lithium (2-methoxy)ethoxide, and crown ethers (47,48). The addition of lithium chloride also promotes the controlled anionic polymerization of 2-vinylpyridine. 

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