Syntheses with organocadmium compounds

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. 

The comparatively low reactivity of organocadmium compounds not only makes the synthesis of ketones possible, but in addition widens the applicability of the method. Organocadmium compounds do not react with many of the functional groups with which the Grignard reagent does react —NO2, —< N, —CO—, —COOR, for example. Consequently, the presence of one of these groups in the acid chloride molecule does not interfere with the synthesis of a ketone (compare with Sec. 15.15). For example ... 

Lithium bromide [1, 604, before references]. This halide markedly promotes the reaction of an organocadmium compound with acyl chlorides (but not with ketones). The effect was used to advantage in the synthesis of a-oxo esters.8... 

Solution Grignard reagents react with dry cadmium chloride to yield the corresponding organocadmium compounds, which react with acid chlorides to yield ketones. To make this concept clearer, the general equation for the synthesis is ... 

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. 

---