Preparation and Properties of Grignard Reagents

Note that there are several modern versions of the Barbier reaction that use transition metals or their derivatives.Examples include indium metal, samarium iodide, and lead. An example using lead reacted benzaldehyde with allyl bromide in the presence of lead metal to give a 99% yield of 45.56 A retro-Barbier fragmentation has also been reported in which an alcohol was treated with 10 equivalents of bromine and 15 equivalents of potassium carbonate in chloroform to give a bromo ketone.5  

In other work, Ashby and co-workers concluded that the RMgX species exists in ether, THE, and triethyl-amine but the composition varies in each solvent. In ether, the monomeric species is largely of RMgX with 

Chapter 8. Nucleophilic Species That Form Carbon-Carbon Bonds 

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