Organic Derivatives of Group lib Metals

In this section, we will discuss organometallics in which the metal is cadmium, mercury, or zinc. Grignard reagents and organolithium compounds can be con- 

For summaries, see P. A. Bartlett, Tetrahedron 36, 2 (1980), especially pp. 15-18, and J. D. Morrison and H. S. Mosher, Asymmetric Organic Reactions, Prentice-Hall, Englewood Cliffs, New Jersey (1976), Chap 3. 

Organomercury and organocadmium compounds are much less reactive than the corresponding lithium or magnesium derivatives, and are therefore useful for certain reactions where selectivity is important. One useful synthetic application of this strategy is the preparation of ketones from acid chlorides and cadmium reagents. Cadmium reagents are useful because they are too unreactive to add to the product ketone, and the reaction therefore stops at the ketone. 

Organomercury compounds have had limited use in synthesis. One promising procedure, based on the availability of the mercury compounds from alkenes via organoboranes, is the synthesis of primary halides from alkenes. This procedure has the opposite regioselectivity to the direct ionic addition of hydrogen bromide 

The most frequently used reaction involving zinc is the Reformatsky reaction, which uses zinc, ethyl bromoacetate, and carbonyl compounds to give (3-hydroxyesters. The reaction by which the organozinc intermediate is formed is presumably similar to that in Grignard reagent formation. The adjacent carbonyl 

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