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Hydrides alkali deprotonation with

Alcohols are commonly deprotonated with either sodium hydride (NaH) or an alkali metal (Na, Li, or K). [Pg.612]

The synthesis of alkali metal organophosphides and arsenides is usually most conveniently achieved by the direct metalation of a primary or secondary phosphine/arsine with a strong deprotonating agent such as an alkyllithium or an alkali metal hydride ... [Pg.35]

An entry into the chemistry of mdo-decaborates is provided by utdo-B oH 4. As already mentioned, decaborane BioHi4 is easily deprotonated even in aqueous medium to yellow B10Hb and with strong bases, such as alkali metal hydrides, even further to the colorless anion B10H122-. This is summarized in the reversible reactions shown in Eq. (59). [Pg.73]

Stepwise deprotonation of methylenebis(triorgano)phosphonium salts with bases yields carbodiphosphoranes via intermediate semi-ylide salts, which may also be accessible by alkylation or phosphinol-ation of corresponding alkylidenephosphoranes (equation 118). " It depends on the starting phosphonium salt and the base whether the intermediate ylide salts can be isolated or not. Suitable bases are sodium amide, alkali metal hydrides, alkylidenetrialkylphosphoranes, potassium and lithium orga-nyls. For the synthesis of hexaphenylcarbodiphosphorane improved methods have been reported by which this compound may be generate without isolation of the ylide salt and on a large scale. [Pg.196]

It is important to consider interactions between NHCs and alkali metals since, in many cases, NHCs are generated by deprotonation of a precursor molecule using an alkali salt of a strong base, such as potassium teri-butoxide, sodium hydride, potassium hydride, or u-butyllithium [19,20]. The influence of alkali metals in solution on stable diaminocarbenes has been investigated by C NMR and it has been postulated that metal ions in solution may act as catalysts for the dimerization of these NHCs [21]. Crystallographically characterized group 1 centers with coordinated neutral NHC ligands, however, are few and far between. [Pg.453]

Alkali metal hydrides such as NaH and KH are also very much used as bases to deprotonate very weak acids. They often allow avoiding the side electron-transfer reactions observed with n-butyllithium in the case of the deprotonation of cations. Finally, t-BuOK (pKa = 28 in DMSO) is a very common base that is used when the... [Pg.293]

Among alkali metal enolates, those derived from ketones are the most robust one they are stable in etheric solutions at 0 C. The formation of aldehyde enolates by deprotonation is difficult because of the very fast occurring aldol addition. Whereas LDA has been reported to be definitely unsuitable for the generation preformed aldehyde enolates [15], potassium amide in Hquid ammonia, potassium hydride in THE, and super active lithium hydride seem to be appropriate bases forthe metallation of aldehydes [16]. In general, preformed alkali metal enolates of aldehydes did not find wide application in stereoselective synthesis. Ester enolates are very frequently used, although they are more capricious than ketone enolates. They have to be formed fast and quantitatively, because otherwise a Claisen condensation readily occurs between enolate and ester. A complication with ester enolates originates from their inherent tendency to form ketene under elimination... [Pg.13]

Amine activatitMi pathway has been well studied in catalysis by lanthanides, early transition metals, and alkali metals. In metal amide chemistry of late transition metals, there are mainly two pathways to synthesize metal amide complexes applicable under hydroamination conditions [54], One is oxidative addition of amines to produce a metal amide species bearing hydride (Scheme 8a). The other gives a metal amide species by deprotonation of an amine metal intermediate derived from the coordination of amines to metal center, and it often occurs as ammonium salt elimination by the second amine molecule (Scheme 8b). Although the latter type of amido metal species is rather limited in hydroamination by late transition metals, it is often proposed in the mechanism of palladium-catalyzed oxidative amination reaction, which terminates the catalytic cycle by p-hydride elimination [26]. Hydroamination through aminometallation with metal amide species demands at least two coordination sites on metal, one for amine coordination and another for C-C multiple bond coordination. Accordingly, there is a marked difference between the hydroamination via C-C multiple bond activation, which demands one coordination site on metal, and via amine activation. [Pg.126]


See other pages where Hydrides alkali deprotonation with is mentioned: [Pg.364]    [Pg.144]    [Pg.89]    [Pg.158]    [Pg.184]    [Pg.43]    [Pg.146]    [Pg.225]    [Pg.486]    [Pg.435]    [Pg.446]    [Pg.171]    [Pg.184]    [Pg.206]    [Pg.107]    [Pg.269]    [Pg.56]   


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Alkali hydrides

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