Abstract
The chiral oxazoline motif is present in many ligands that have been extensively applied in a series of important metal-catalyzed enantioselective reactions. This Review aims to provide a comprehensive overview of the most significant applications of oxazoline-containing ligands reported in the literature starting from 2009 until the end of 2018. The ligands are classified not by the reaction to which their metal complexes have been applied but by the nature of the denticity, chirality, and donor atoms involved. As a result, the continued development of ligand architectural design from mono(oxazolines), to bis(oxazolines), to tris(oxazolines) and tetra(oxazolines) and variations thereof can be more easily monitored by the reader. In addition, the key transition states of selected asymmetric transformations will be given to illustrate the features that give rise to high levels of asymmetric induction. As a further aid to the reader, we summarize the majority of schemes with representative examples that highlight the variation in % yields and % ees for carefully selected substrates. This Review should be of particular interest to the experts in the field but also serve as a useful starting point to new researchers in this area. It is hoped that this Review will stimulate both the development/design of new ligands and their applications in novel metal-catalyzed asymmetric transformations.
Highlights
Ligands containing a chiral oxazoline are some of the most successful, versatile, and commonly used ligand classes in asymmetric catalysis due to their ready accessibility, modular nature, and applicability in a wide range of metal-catalyzed transformations.The vast majority of these ligands are formed in short, high yielding synthesis from readily available chiral β-amino alcohols
This review reports on the use of such ligands in homogeneous metal-catalyzed asymmetric synthesis since 2009, when the area was last reviewed by us.[1]
This Review reports on further developments in the design and application of oxazoline-derived ligands in asymmetric catalysis over a 10-year period since 2009, when the area was previously reviewed by us
Summary
6492 6493 6495 6495 6498 6503 6504 6504 6504 6504 6504 6504 6505 6505 6505 the significance of research related to the term “oxazoline” (Figure 1). This review reports on the use of such ligands in homogeneous metal-catalyzed asymmetric synthesis since 2009, when the area was last reviewed by us.[1] This review does not cover the application of such ligands in heterogeneous systems or in the synthesis of polymers. In our view, the most significant applications of oxazoline-containing ligands reported in the literature until the end of 2018. This review will be structured in the same manner as our 20042 and 2009 reviews 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. The key transition states of selected asymmetric transformations employing metal complexes of oxazoline ligands will be given to illustrate the features that give rise to high levels of asymmetric induction. As a further aid to the reader, we summarize the majority of schemes with representative examples which highlight the variation in % yields and % ees for carefully selected substrates
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