Reaction with Polar Organometallics

Perhaps carboxylation is the most frequently applied reaction with polar organometallic derivatives. Yields are mostly excellent and purification can be carried out conveniently via the water-soluble alkali metal salts, and subsequently, in many cases, by crystallization ... 

Although no generally applicable experimental rules can be given for controlling the regiochemistry of reactions with polar organometallic derivatives and a,/ -unsaturated compounds, some trends and regularities can be observed ... 

Reactions of polar organometallic and Grignard reagents with a-haloethers generally proceed much more easily than the familiar SN2 displacements with alkyl halides. This may be explained by the large extent of Sjql character due to the ionization ... 

There are no systematic studies on the reaction of sulfur dichloride with polar organometallic reagents. The high reactivity of sulfur dichloride allows the couplings to be carried out at very low temperatures, even at —100 °C the reactions proceed almost instantaneously. The use of an excess of SC12 should be avoided, since this reactive molecule may easily add to the hetero-aromatic system or form an (unstable) sulfonium compound with the sulfur between the two heterocyclic units. 

We begin with reactions of polar organometallics with aldehydes, ketones, and v/c-dicarbonyl compounds (a-oxoaldehydes, 1,2-diketones, a-oxocarboxamides, and a-oxocarboxylic acids). Next we focus on carboxamides, lithium carboxylates, carboxylic acid esters, and acyl chlorides. Finally we turn to ketenes, (thio)isocyanates, and carbon dioxide, all featuring cumulated double bonds, and last but not least to carbon monoxide. 

Nitriles are similar in some respects to carboxylic acids and are prepared either by SN2 reaction of an alkyl halide with cyanide ion or by dehydration of an amide. Nitriles undergo nucleophilic addition to the polar C=N bond in the same way that carbonyl compounds do. The most important reactions of nitriles are their hydrolysis to carboxylic acids, reduction to primary amines, and reaction with organometallic reagents to yield ketones. 

Organomercury compounds, reaction with NaBH4, 222 Organometallic compound, 345 polarity of, 143... 

The polarity of carbon-halogen bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Nucleophilic substitution reactions are categorised into and on the basis of their kinetic properties. Chirality has a profound role in understanding the reaction mechanisms of Sj l and Sj 2 reactions. Sj 2 reactions of chiral all l halides are characterised by the inversion of configuration while Sj l reactions are characterised by racemisation. 

A number of transmetalation procedures leading to zinc organometallics can be performed. Many organometallics having a polar C—Met bond are readily transmetalated by the reaction with a zinc salt to the more covalent organozinc compounds. The synthetic... 

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