Organocadmium reagents preparation

The most common application of organocadmium compounds has been in the preparation of ketones by reaction with acyl chlorides. A major disadvantage of the use of organocadmium reagents is the toxicity and environmental problems associated with use of cadmium, and this has limited the recent use of organocadmium reagents. 

The configuration at the remaining asymmetric center in a-erythro-idine, C-12, was determined by Hill and Schearer (21) who took advantage of the Hofmann degradation sequence carried out earlier (Fig. 4) which had yielded the dextrorotatory ketone XVII (-I- )-XVII was synthesized by reaction of the organocadmium reagent from o-bromoethyl-benzene with the acid chloride from (-I- )-tetrahydrofuran-3-carboxylic acid (LI). The configuration of LI was then established by conversion to (4-)-3-methyltetrahydrofuran which was also prepared from R - -)-... 

The acylation reaction has been applied successfully to the preparation of various polyfunctional natural ketones. Thus, lactarinic add was obtained in high yield (Scheme 13.19). It should be noted that a similar synthesis via the acylation of organocadmium reagent affords lactarinic add in only 30% yield [17]. 

The main use of organocadmium compounds is for the preparation of ketones and keto-esters, and their special merit lies in the fact that they react vigorously with acid chlorides of all types but add sluggishly or not at all to multiple bonds (compare addition of Grignard reagents to carbonyl groups). Some t3rpical syntheses are ... 

Organocadmium compounds are normally prepared from the appropriate Grignard reagents ... 

Organocadmium compounds may be prepared by the action of anhydrous cadmium chloride upon the corresponding Grignard reagents, for example ... 

Organocadmium compounds can be prepared from Grignard reagents or organo-lithium compounds by reaction with Cd(II) salts.180 They can also be prepared directly from alkyl, benzyl, and aryl halides by reaction with highly reactive cadmium metal generated by reduction of Cd(II) salts.181... 

Organocadmium compounds can be prepared from Grignard reagents or organo-lithium compounds by reaction with Cd(II) salts.136 Organocadmium compounds can also... 

Many organocadmium compounds are known but few have been of commercial importance. Wanklyn first isolated diethyl cadmium in 1856. The properties of this and other dialkylcadmiums are listed in Table 4. In general, these materials are prepared by reaction of an anhydrous cadmium halide with a Grignard or alkyUithium reagent followed by distillation of the volatile material in an inert atmosphere or in vacuo. Only the liquid dimethyl compound is reasonably stable and then only when stored in a sealed tube. Dimethylcadmium is mildly pyrophoric in air and produces dense clouds of white, then brown, cadmium oxide smoke, which is highly toxic if breathed (45). When dropped into water, the liquid sinks in large droplets that decompose with a series of small explosive jerks and pops. For this reason, and particularly because of the low thermal stability, most dialkylcadmium materials are prepared and used in situ without separation, eg, in the conversion of acid chlorides to speciality ketones (qv) ... 

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. 

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