Grignard reagent with cadmium chloride

Cadmium alkyls, obtainable from Grignard reagents and cadmium chloride,329 also lead to ketones when treated with acid chlorides ... 

Grignard reagents derived from aryl bromides are readily prepared and may be converted into organocadmium compounds by treatment with cadmium chloride (cf. Section 5.8.4, p. 616). Reaction of an organocadmium with a carboxylic acid chloride constitutes a convenient synthesis of aryl alkyl ketones. 

Aryl tellurium halides react with aliphatic and aromatic Grignard reagents, with ethenyl magnesium halides , with ethynyl magnesium bromide with dimethyl and diethyl cadmium , with 2-(diphenylphosphino)-phenyl lithium, and with phenyl mercury chloride to produce aryl organo telluriums (p. 416). 

In this ketone synthesis, (1) the Grignard reagent reacts with cadmium chloride to yield an organocadmium compound, plus a magnesium dihalide. (2) The organocadmium is then reacted with an acid chloride to yield a ketone plus cadmium chloride. 

Grignard reagents maybe used to prepare other organometaUic reagents, for example, ethylmagnesium bromide reacts with cadmium chloride to yield diethylcadmium ... 

These materials, generally prepared from the corresponding Grignard reagents by the addition of cadmium chloride, provide a milder reagent system than the Grignard that allows selectivity in reaction with phosphorus trichloride (Equation 4.21).34-43-63... 

X-5 The reaction of a cadmium Grignard reagent (R2Cd) with an acid chloride. This reaction requires the formation or a cadmium Grignard which can be formed as shown below... 

Grignard reagents react with dry cadmium chloride to yield the corresponding organocadmium compounds, which react with acid chlorides to yield ketones ... 

There are two ways round this problem. One is to use a less reactive organometallic reagent which reacts with acid chlorides but not with the less reactive ketones. Cadmium is a good metal for this purpose and the reagents (2) can be made from Grignard reagents or organolithiums. 

Dimethylcadmium A solution of methylmagnesium bromide (0.3 mole) is prepared as usual from methyl bromide and magnesium. It is then cooled in ice and treated slowly with finely powdered, anhydrous cadmium chloride (0.16 mole). The ice-bath is then removed and the mixture is stirred for 0.5 h. Finally the color test (page 879) is applied to make sure that the Grignard reagent has been wholly consumed. 

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