G. Hargaden, P. Guiry
Apr 20, 2009
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Chemical reviews
Abstract
Compounds containing a chiral oxazoline ring have become one of the most successful, versatile, and commonly used classes of ligands for asymmetric catalysis due to their ready accessibility, modular nature, and applicability in a wide range of metal-catalyzed transformations. The large majority of these ligands are derived from readily available chiral amino alcohols in short, high yielding synthetic sequences. As a consequence, the enantiocontrolling stereocenter resides on the carbon atom neighboring the coordinating nitrogen of the oxazoline ring and, therefore, in close proximity to the metal active site, thus having a direct influence on the stereochemical outcome of the reaction. Since the first report in 1986 of the use of chiral oxazolinebased ligands in asymmetric catalysis, a diverse range of ligands with one, two, or more oxazoline rings incorporating various heteroatoms, additional chiral elements, and specific structural features have been used with great success in a wide range of asymmetric reactions. This review reports on the use of such ligands in homogeneous metal-catalyzed asymmetric synthesis since 2004, when the area was last reviewed.1 We cover, to the best of our knowledge, all applications of oxazolinecontaining ligands reported in the literature until the end of 2007. This review will be structured in the same manner as our 2004 review, as we classify ligands not by the reaction to which their metal complexes have been applied but by the nature of the denticity, chirality, and donor atoms involved. In this manner, the continued development of ligand architectural design can be more easily monitored.