Science of Synthesis

Heaney, H.; Christie, S., Science of Synthesis, (2004) 3, 317.

Grignard reagents, including arylmagnesium halides, react with a wide variety of substrates, but it is remarkable how frequently dramatic improvements in yields have been observed when either a catalytic or a stoichiometric amount of a copper(I) salt is added to the reaction mixture. In some reactions the regiochemistry changes when organocopper intermediates are involved. The most well-known examples of this latter effect are observed in the conjugate addition reactions of α,β-unsaturated carbonyl compounds. The ease of formation of a large number of Grignard reagents from aryl halides is a major attraction for the use of that class of organometallic precursors to organocopper intermediates. This section deals with the use of aryl Grignard reagents and it can be divided into a number of subsections. They are (1) reactions that involve the presence of a catalytic amount of a copper(I) salt, (2) reactions that involve a neutral arylcopper(I) species, (3) reactions carried out in the presence of chlorotrimethylsilane, and (4) reactions carried out in the presence of aluminum chloride and other Lewis acids. In a fifth possibility, where the stoichiometry involves two equivalents of the Grignard reagent to one equivalent of a copper(I) salt, the copper carries a formal negative charge and as such the copper(I) species is present as an “ate” complex. The reactions that involve cuprates will be dealt with in Sections ‌3.4.6‌ and ‌3.4.7‌.

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References

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• 8.Meeeee-Meee, (8888) 8/8e, 888.
• 8.Meeeee-Meee, (8888) 88/8, 888.