Metal-template electrophilic substitution on phenols: Synthesis and crystal structure of bromomagnesium phenolate and its reactive complex with para-isopropylbenzaldehyde

The crystal structures of the bromomagnesium phenolate 5 and its complex 7 with para-isopropylbenzaldehyde are reported; for the first time it has been possible to demonstrate that the reactive complex 7, responsible for the complete ortho-regioselective control in the alkylation of phenoxymagnesium bromides with aldehydes, is not obtained by simple replacement of the ethereal ligand but by expansion of the metal coordination sphere from 4 (usual tetrahedral configuration) to 5. We infer from H-1 NMR studies that the magnesium coordination of complex 7 in solution is analogous to that shown in the solid state, with a complexed ethereal molecule.