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2.4.5 Method 5: Synthesis of Tricarbonylmetal–Arene Complexes by Arene Modification

DOI: 10.1055/sos-SD-002-00214

Kündig, E. P.; Pache, S. H.Science of Synthesis, (20032165.

Coordination to a tricarbonylmetal group induces profound changes in the reactivity of the coordinated arene, both at the ring and at benzylic positions. To date, this has been demonstrated and used only in chromium complexes. The dominant feature of the tricarbonylchromium group is that of an electrophilic auxiliary. It inverses the reactivity of a complexed arene, renders the ring carbons susceptible to nucleophilic attack, and increases the acidity of ring and benzylic hydrogens. However, the tricarbonylchromium group also has donor properties and is capable of stabilizing a benzylic cation. This duality in function has led to widespread use of (arene)tricarbonylchromium complexes in organic synthesis. The steric blocking of one face of the arene by the tricarbonylchromium fragment, and the resulting control of stereochemistry, adds yet another powerful feature to these reactions. Transformations that result in new tricarbonylchromiumarene complexes are discussed below or, if they result in optically active complexes, in Section 2.4.7. Reactions that involve modifications of the arene side chain are presented in Section 2.4.6, and those that give products other than new (arene)tricarbonylchromium complexes will be discussed in Section 2.4.10.