Lithium, alkyls complexes

These alkene isomers are separately available (4) by treatment of threo-S-trimethylsilyloctan-4-ol, prepared by reduction of the corresponding ketone with DIBAL in pentane at —120°C, with base or acid. The preparation of 5-trimethylsilyloctan-4-one itself illustrates three general procedures the addition of alkyl lithium reagents to vinylsilanes to generate a-lithiosilanes, the preparation of complex /5-hydroxysilanes, as diastereoisomeric mixtures, and the oxidation of such compounds to /8-ketosilanes... 

The tetraimidosulfate anion [S(NtBu)4]2 is obtained, as the dilithium derivative 61, by the reaction of S(NtBu)3 with two equivalents of LiM I Bu.175 The nucleophilic addition of sterically undemanding alkyl-lithium reagents, e.g., MeLi, to S(N Bu)3 produces the dimeric complex [(thf)2Li2 (NtBu)3SMe 2] (62).174 A, A -chelated complexes of the [MeS(NlBu)3] anion are obtained by the nucleophilic addition of Me2Zn or Me3Al to S(NlBu)3.176... 

Enantiocontrol using alkyl lithium-chiral coordinating agent complex... 

The chelate formation in lithium complexes 17 or 20 contributes to stabilization. Enhancement of kinetic acidity arises from the formation of pre-complexes 16 and 19, respectively. Here, already a dipole is induced and, in addition, proton exchange can proceed intramolecularly via a five- or six-membered ring. Despite these favourable features, the acidity of alkyl carbamates 15 is lower than those of the 1-proton in butane n-BuLi does not lead to deprotonation. In order to suppress carbonyl attack, a branched amino residue NR2 such as diisopropylamino (in Cb) or 2,2,4,4-tetramethyl-l,3-oxazolidin-3-yl (in Cby) is essential. A study on the carbenoid nature of compounds 17 was undertaken by Boche and coworkers. ... 

This review describes the preparation, characterization, and properties of all nonpolymeric complexes that contain a metal removed from the fullerene also are included. The article does not cover the essentially ionic fullerides MmC (4) or the endohedral metallofullerenes MmC (8), which have been reviewed previously. The extended fullerenes, or so-called carbon nanotubes, which have hollow centers and can be filled with metal salts, also are not discussed. The majority of complexes involve 7r-bonds and, apart from alkyl lithium fullerides, the potentially useful synthetic area of o- complexes has not been explored. Table I shows the occurrence of metal-bound adducts across the periodic table. 

In a parallel study, Wipf and Fritch11041 have shown that also urethane-protected (Boc), and even amino acid segments, are tolerated as acyl compounds on the aziridine nitrogen. The best results were obtained with alkylcopper reagents derived from CuCN and an alkyl-lithium in the presence of boron trifluoride-diethyl ether complex. Some 6-alkylated compounds (11-15%) were isolated as well. This work was extended to a solid-phase procedure that resulted in resin-bound alkene isosteres that could immediately be used in further peptide synthesis.11051 For this purpose, the 2-nitrophenylsulfonyl (oNbs) group was used for nitrogen protection and aziridine activation. It could be readily cleaved with benzenethio-late, which was compatible with the acid-sensitive Wang linker used. 

The base used may be hydroxide, alkoxide, carbonate, alkyl lithium, or alumina (13, 20, 24, 41, 49). The reaction is the reverse of the vinylidene synthesis by protonation of the n-acetylide, and the two complexes form a simple acid-base system. For the iron complexes in Eq. (2), the pK has been measured at 7.78 (in 2 1 thf-H20) (24). 

Buchachenko (1974) has advanced another theory. He based his reasoning on the absence of the CIDNP signals for the reaction of //-butyl iodide with t-butyl lithium conducted in ether at -70°C. The halogen and metal quickly exchange under these conditions, but the C—C bond does not form. In contrast to the preceding scheme, Buchachenko s theory assumes that the radicals produced form complexes with the alkyl lithium associates. Alkyl... 

According to this study54, one model for studying the complex reactions of alkyl lithium compounds, involving aggregation and interactions with the solvent molecules, could be the reaction between vinylamine and LiH. The complex formed between lithium... 

The lithium amidinates are used as precursors for homoleptic lanthanide amidinates. Lanthanide amidinate complexes have a high catalytic activity in the polymerization of ethylene. They are also used in the manufacture of membranes. Lanthanide amidinate complexes 37 (La=Er, Y, Gd) are also obtained from alkyl metal complexes 36 and... 

Ruff et al. in a series of publications described the synthesis of amine complexes of aluminum hydride [32, 33]. Their study investigated the reaction of these materials with typical Lewis bases in order to define the conditions for the stability of aluminum hydride derivatives in which the aluminum atom exhibits a coordination number of five. They first described methods for making tertiary alkyl amine complexes of aluminum hydride utilizing lithium aluminum hydride and an amine hydrochloride. A finely ground lithium aluminum hydride was placed together with trimethylammonium chloride (ratio 1 2). They prepared other trialkylamine alanes and the N-dialkylaminoalanes, in a similar fashion. These adducts of alane were found to sublime readily at temperatures up to 40 °C except for the tri-n-propylamine alane, which sublimed very slowly and could also be recrystallized from hexane at — 80 °C. 

The dependence of the propagation rate on initiator concentration is more complex, however, and can be explained as reflecting the existence of more than one kind of active center in media that can solvate the counterion. The simplest situation, which is used here for illustration, corresponds to an equilibrium between free ions and ion pairs. [It is likely that various kinds of ion pairs exist (cf. Eq. 9-1) but these ramifications can be neglected in this simple treatment.] The reactions involved in the actual propagation steps in the polymerization of a monomer M by an alkyl lithium compound RLi can then be represented as... 

Oxidative addition of the carbon-halogen bond is a well-documented reaction for Group 10 transition metal complexes, but it is relatively limited for ruthenium. The example given here involves the reversible oxidative addition of allyl halide to RuCp(CO)2X to produce RuCp(p -allyl)X2 [78]. Oxidative addition of allyl halide to a Ru(0) complex Ru(l,5-COD)(l,3,5-COT) is also reported, but the product yield was poor [79]. Nevertheless, a catalytic Heck-type alkenylation of bromostyrene with methyl acrylate by Ru(l,5-COD)(l,3,5-COT) proceeded smoothly [80]. A cross-coupling reaction of alkenyl halide with Grignard reagents or alkyl lithium also pro-... 

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