Lithium and magnesium

Some of the chemical properties of Li that make it diagonally related to Mg rather than vertically related to the other alkali metals are summarized overleaf 

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The properties of the head element of a main group in the periodic table resemble those of the second element in the next group. Discuss this diagonal relationship with particular reference to (a) lithium and magnesium, (b) beryllium and aluminium. 

From a synthetic point of view, direct alkylation of lithium and magnesium organometallic compounds has largely been supplanted by transition-metal-catalyzed processes. We will discuss these reactions in Chapter 8 of Part B. 

One of the major advantages of 2-alkenylpotassium derivatives over the appropriate lithium and magnesium analogs is the possibility of controlling the double-bond configuration in the allylie anion. For instance, the geometry of ( )-2-butene is retained in the e.vu-2-butenyl anion below — 50 0C, but equilibration above - 25 C leads to the endo-crotyl anion with >97% selectivity12. 

Chiral imines derived from 1-phenylethanone and (I. Sj-exo-l, 7,7-trimethyIbicyclo-[2.2.1]heptan-2-amine [(S)-isobornylamine], (.S>1-phenylethanamine or (R)-l-(1-naphthyl) ethanamine are transformed into the corresponding (vinylamino)dichloroboranes (e.g., 3) by treatment with trichloroborane and triethylamine in dichloromethane. Reaction of the chiral boron azaenolates with aromatic aldehydes at 25 "C, and subsequent acidic hydrolysis, furnishes aldol adducts with enantiomeric excesses in the range of 2.5 to 47.7%. Significantly lower asymmetric inductions are obtained from additions of the corresponding lithium and magnesium azaenolates. Best results arc achieved using (.S )-isobornylamine as the chiral auxiliary 3. 

The zinc chloride is acting here as a Lewis acid. Similarly, thiirane dioxides react with metal halides such as lithium and magnesium chlorides, bromides and iodides in ether or THF to give the halo-metal sulfmates (130) in fair yields157. 

Seyferth prepared a-halogenoalkyl-lithium and -magnesium compounds by treating the appropriate gem-dihalides with butyllithium or with Grignard reagents at low temperature, and then used the products to prepare acyclic and cyclic a-halogenoalkyltin compounds (57-60). Typical examples are shown in the following equations. 

The aim of this chapter is to review the chemistry of chalcogenolates in the last 10 years. The more recent reviews in this field included chalcogenolates of the s-block elements,13,14 early transition metal thiolates,15 metal complexes with selenolate and tellurolate ligands,16 copper(I), lithium and magnesium thiolates,17 functionalized thiolate complexes,18 19 pentafluorobenzenethiolate platinum group compounds,20 tellurium derivatives,21 luminescent gold compounds,22 and complexes with lanthanide or actinide.23... 

Alkane elimination is readily used for lithium and magnesium organometallic compounds... 

Electron ionization (El) was introduced in 1921 by Dempster, who used it to measure lithium and magnesium isotopes [31]. Modern El sources are, however, based on the design by Bleakney [32] and Nier [33, 34], who both worked in Prof. J. T. Tate s laboratory. In El ions are produced by directing an electron beam into a low pressure vapor of analyte molecules. 

The compounds of lithium and magnesium are the most important of the group IA and IIA organometallics from a synthetic perspective. The metals in these two groups are the most electropositive of the elements. The polarity of the metal-carbon bond is such as to place high electron density on carbon. This electronic distribution is responsible for the strong nucleophilicity and basicity of these compounds. 

In 1993, Satoh and coworkers reported the preparation of lithium- and magnesium-aUtylidene carbenoids from 1-chlorovinyl phenyl sulfoxides by sulfoxide-metal exchange reaction at low temperature (Scheme 6). 1-Chlorovinyl phenyl sulfoxide (128) is easily synthesized from the corresponding aldehyde and chloromethyl phenyl sulfoxide in high yield. Sulfoxide 128 was treated with f-BuLi in THF at —78 °C to give the terminal alkyne 131. Obviously, the intermediate of this reaction was the alkylidene carbenoid 129. 

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