Halide From ketone

TMG (1) or BTMG (2) participate in the preparation of vinyl halides from hydrazones and halogen molecules [96]. Examples of the two-step synthesis of vinyl halides from ketones through hydrazones are shown in Table 4.15 [96a]. This procedure has been frequently employed in chemical synthesis and often provides alternative access to vinyl iodide difficult to prepare otherwise. 

Table 4.15 Two-step synthesis of vinyl halides from ketones through hydrazones...

N-Chlorosuccinimide sodium alcohol Halides from ketones with C-cleavage... 

Answer This branched primary amine can be made from ketone (21) via the oxime (p T 63). A 1,2 C-C disconnection on (21) is good as it needs the symmetrical allylic halide (22). 

Organometallic compounds or carbanions undergo a number of reactions in which the carbanion or carbanion-like moiety of the organometallic compound acts as a nucleophilic displacing agent. Examples are the formation of hydrocarbons from alkyl halides, alkyl halides from halogens, and ketones from acid chlorides or esters. The latter two reactions are closely related to the base-catalyzed condensations and are perhaps additions as well as displacement reactions. Related addition reactions are the carbonation of organometallic compounds and the addition to ketones or aldehydes. 

Scheme 83 Nickel-catalyzed formation of ketones and acid halides from carbon dioxide and aryl or vinyl halides.

The a-alkylation of enolates derived from ketones with alkyl halides is a very important and frequently used method for forming new carbon-carbon bonds in organic synthesis [40]. Yet, if the a-alkylation of enolates derived from ketones with alkyl halides can be replaced by the direct reaction of ketones with alcohols, this method would provide a very useful waste-free, green route to a-alkylation, producing no side products other than water. 

A considerable number of examples will be found in the text in which halo-genated and other substituted olefins are produced. Their modes of formation do not usually differ in principle from the corresponding unsubstituted case. However, some special methods have been used, for example, the direct preparation of halo olefins from ketones with phosphorous halides, or via hydrazones. 

Thiochrom-4-ones have also been prepared by the amine-promoted elimination of hydrogen halide from 3-haIothiochroman-4-ones,188 by the Puinmerer reaction on thiochroman-4-one S-oxides [Eq. (20)],98 from a ring expansion of activated benz[6]thiophenes [Eq. (21)],189 by the reaction of o-mercaptoaryl alkyl ketones with ethyl esters of... 

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