Deprotonative metalation combinations

DEPROTONATIVE METALATION USING ALKALI METAL-NONALKALI METAL COMBINATIONS... 

Sn6garoff K, Komagawa S, Chevallier F et al (2010) Deprotonative metalation of substituted benzenes and heteroaromatics using amino/alkyl mixed lithium-zinc combinations. Chem Eur J 16 8191-8201. doi 10.1002/chem.201000543... 

Dayaker G, Sreeshailam A, Chevallier F et al (2010) Deprotonative metallation of ferrocenes using mixed lithium-zinc and lithium-cadmium combinations. Chem Commun 46 2862-2864. doi 10.1039/b924939g... 

When lithiated, the ring strain of the three-membered heterocycle remains important, and this strain, combined with a weakening of the a-C-O bond, due to its greater polarization, make metalated epoxides highly electrophilic species [2], They react with strong nucleophiles (often the base that was used to perform the a-deprotonation) to give olefins following the elimination of M2O (Scheme 5.2, Path B), a process often referred to as reductive alkylation . 

When a metal oxide surface is exposed to water, adsorption of water molecules takes place as shown in Equation 2.1. Cation sites can be considered as Lewis acids and interact with donor molecules like water through a combination of ion-dipole attraction and orbital overlap. Subsequent protonation and deprotonation of the surface hydroxyls produce charged oxide surfaces as shown in Equation 2.2 and Equation 2.3, respectively ... 

The trilluoromethyl group behaves in a similar way , but it is now clear that deprotonation of sites ortho to such acidifying but non-coordinating and non-electrophilic substituents is best carried out with BuLi-KOBu-t superbases (see Section VI). A combination of BuLi metallation and superbase metallation of fluoroarenes has been used in the synthesis of components 163 and 164 for fluorinated liquid crystals (Scheme 82). ... 

The combination of an alkyllithium with a metal aUcoxide provides a marked increase in the basicity of the organolithium . The most widely used of these superbases is the one obtained from BnLi and KOBu-t, known as LiCKOR (Li—C + KOR) °. The exact natnre of the prodncts obtained by snperbase deprotonations—whether they are organolithinms, organopotassiums, or a mixtnre of both—is debatable, as is the precise nature of the superbase itself. For example, while prolonged mixing of alkyllithium and... 

Activated methylene components like malonic esters and P-ketoesters can be coupled anodically using small amounts of potassium iodide as redox catalyst (Table 4, No. 4-7) i45-i5n -pj g cathodically formed metallic potassium is used to deprotonate the methylene component generating the oxidizable carbanion. The combination of this reaction with the cathodic hydrodimerization of acrylic esters has been studied several times (Table 4, No. 7) Thus both electrode reac-... 

Metal ions such as Rh(III), Ir(III), Pd(II), Pt(II) and Pt(IV) may be used, although pyridyl-type ligands are less appropriate in these cases since they do not provide the required orbital energy levels. In such cases, combinations of pyridyl and N—C carbanion ligands, such as deprotonated 2-phenylpyridine, are beginning to prove useful. 

Methylation, in combination with metal coordination, can occasionally lead to dramatic alterations in pK.t values, with shifts > 12 units. Such a case is realized with a Pt(II) complex of 1,9-DiMeA (260) While in 9-MeA the exocyclic amino group deprotonates with pK.t 16.7, in l,9-DiMeAH+ this deprotonation occurs with pAa = 9.1, and in the Pt(II) complex fra/ ,v- (NH3)2Pt( 1,9-DiMeAH-/V7)2]4+ the pV, values further drop to 6.4 (pVl2) and 4.1 (pAal). As discussed in more detail in Section VI, neighbor group effects account in part for this acidification. 

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