on the occasion of his 60th birthday
The development of functionnalized organometallic compounds is a dramatically growing field, and considerably broadens the scope of these nucleophilic reagents. [1] An important breakthrough in the preparation of these reactive species, which contain sensitive functional groups, has been the discovery of alternative synthetic pathways to the Grignard or Barbier oxidative addition of activated metals to organic halides, such as halogen-metal exchange [2] or new selective-metalation processes. [3] Both approaches enable the preparation of numerous functional organometallic reagents, and are powerful tools, especially in the field of aromatic or heterocyclic chemistry. [4] Using these methods, which are based on the selective formation of a carbonÀmetal bond in the presence of sensitive functional groups, the metallic bond is established after the functional groups are introduced. However, one can conceive an alternative strategy, with the formation of the metallic bond prior to functional group introduction. Such an approach is only possible if the carbonÀ metal bond is kinetically and/or thermodynamically stable enough to withstand functional group manipulations. As a matter of fact, numerous examples of such a strategy have recently been reported using organoboron or organotin reagents, which shows that several synthetic transformations can be conducted on remotely embedded functional groups of these compounds. [5] If one considers the difference in electronegativity between a metal and a carbon atom as an empirical criterion for the development of functionalized organometallic compounds, as proposed by Knochel and co-workers in their seminal review on this field, [6] it is striking to see that the carbonÀaluminum bond can be located between the carbonÀ zinc and the carbonÀmagnesium bond, which are two very