Lithium salts, role

This complex is not the actual catalyst for the hydrovinylation, but needs to be activated in the presence of a suitable co-catalyst. The role of this additive is to abstract the chloride ion from the nickel centre to generate a cationic allyl complex that further converts to the catalytically active nickel hydride species. In conventional solvents this is typically achieved using strong Lewis acids such as Et2AlCl. Alternatively, sodium or lithium salts of non-coordinating anions such as tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate (BARF) can be used to activate hydrovinylation... 

Lithium salts of resonance-stabilized organic anions have also found a role in carbon-phosphorus bond formation by displacement at phosphorus. The generation of the lithium salt derived from acetonitrile (or other aliphatic nitriles by reaction with butyl lithium or lithium diisopropylamide) provides for carbon-phosphorus bond formation by displacement of halide from phosphorus (Equation 4.24).68... 

The presence of lithium salts plays an important role in the stereochemistry of these... 

Manna V [Bipolar affective disorders and role of intraneuronal calcium. Therapeutic effects of the treatment with lithium salts and/or calcium antagonist in patients with rapid polar inversion]. Minerva Med 82 757-763, 1991... 

The role of alkali metal cations in the [ RuCL(p-cymene) 2l-pseudo-dipepLide-catalysed enantioselective transfer hydrogenation of ketones with propan-2-ol has been examined. Lithium salts were shown to increase the enantioselectivity of the reaction when 2-PrONa or 2-PrOK was used as the base. An alternative reaction mechanism for the pseudo-dipeptide-based systems, in which the alkali metal cation is an important player in the ligand-assisted hydrogen-transfer step, has been proposed.370... 

Addition of the ylide to the carbonyl is postulated to lead first to the zwitterionic intermediate betaine, which would then close to form a four-membered cyclic intermediate, an oxaphosphetane. The existence of the betaine hasn t been fully established, although its intermediacy plays an important role in the Schlosser Modification. Betaines may be stabilized by lithium salts leading to side products therefore, suitable bases in the Wittig Reaction are for example NaH, NaOMe, NEt3). 

Esters, and Alkyl Carbonate Solutions Containing Lithium Salts, and the Role of Atmospheric Contaminants (02, H20, C02)... 

In addition to this, there is another lithium salt promoted pathway (Fig. 4.9) that contributes signihcantly to product formation. Here the product-forming reaction between lithium acetate and acetyl iodide is followed by the reaction between Lil and methyl acetate. These reactions are shown by the inner loop on the left-hand side. In fact, the inner loop is the dominant product-forming pathway, and lithium salts play a crucial role in the overall catalysis. Note that the right-hand-side loop of the catalytic cycle is exactly the same as in Fig. 4.1(a). 

Mukaiyama and co-workers revealed that Li salts play a significant role in controlling the novel stereochemical preference that is involved in the glycosidation with ribofur-anose derivatives (Sch. 52). In particular, LiC104 [101-105] and LiNTf2 [105] were found to be effective additives in the stereocontrolled synthesis of a-o-ribofuranosides from 2,3,5-tri-O-benzyl-D-ribofuranose and several alcohols, whereas p anomers were formed in the absence of the lithium salts. Sch. 52 shows several examples that emphasize general characteristics with or without the addition of lithium salts. In the most recently advanced system (Sch. 53), a hypothetical mechanism of this reverse stereocontrol to yield 110 with the influence of lithium salt is also discussed. In the presence of 10 mol % TrC104, both pure a anomer 110 (a /3 = >99 <1) and P anomer 111 a-.p = <1 >99) isomerized to afford a P anomer-rich mixture (a p = 6 94). 

A variety of dimensionally stable solid electrolytes consisting of a mixture of organic plasticizers such as EC, PC etc., along with structurally stable polymers such as poly( acrylonitrile) (PAN) or poly( vinyl sulfone) (PVS), or polyvinyl pyrrolidine (PVP) or polyvinyl chloride (PVC) and several lithium salts have been tested and found to have excellent ionic conductivities at ambient temperatures [155-156]. In these gel type electrolytes the primary role of the polymers PAN, PVS, PVP or PVC is to immobilize the lithium salt solvates of the organic plasticizer liquids. However, with polymers such as PAN a coordination interaction with Li+ is also quite likely. 

The unusual properties of polytertiaryamine chelated lithium salts have been noted (6). The high solubility and conductivity of chelated lithium halides in benzene raise a number of important and interesting questions concerning the role of the aromatic solvent since these chelated... 

Anhydrous lithium salts are soluble in organic solutions which can be considered to be air-stable catalysts. The most common is lithium perchlorate which is generally used in solution in diethyl ether (LPDE) [9], nitromethane [15], and dichloro-methane [16]. Its catalytic role comes from the properties of the lithium cation [17] which gives rise to specific solute-Liinteractions modulated by complexation to appropriate solvents and counterions [18]. A recent proposal denies lithium catalysis and emphasizes electrostatic stabilization of the transition state by LPDE... 

Among monoamines, both enantiomers of 1-phenylethylamine and their derivatives play a prominent role. They are commercially available, but can also be prepared by resolution of the racemate, obtainable by Leuckart- Wallach reaction of acetophenone1, with malic acid2 or, more conveniently, with tartaric acid in methanol3. They are used as chiral additives for the addition of zinc alkyls to aldehydes in Section D. 1.3.1.4., as copper complexes for the synthesis of biaryls in Section B.2., as lithium salts for enantioselective deprotonation in Section C., and as imines in Sections D.1.1.1.3.1., D.1.1.1,4.. D.1.4.4., D.1.5.2., D.1.5.8., D. 1.6.1.2.1., D.2.3.I., and D.8. A general procedure for the synthesis of imines from carbonyl compounds and primary amines, with many examples of both chiral carbonyl compounds and chiral amines is given in reference 4. 

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