Carbenes, oxazoline units

Finally, two chiral monodentate N-heterocyclic carbene ligands that contain an oxazoline unit have been reported. Glorius et al. reported the synthesis of the imidazolium salts 76 by cyclizing the corresponding bisoxazolines 75 (Scheme 50) [133]. 

Bidentate N-Heterocyclic Carbene Ligands Incorporating Oxazoline Units I 327... 

In 1998, Herrmann et al. reported the synthesis of the first chiral carbene containing an oxazoline unit. In this bidentate ligand, the oxazoline ring is linked in its 2-position to the imidazole ring via a methylene bridge [48]. The key step in the synthesis of the imidazolium precursor is the acid-catalyzed cyclization of the oxazoline by reaction of an iminoester, formed in situ from a nitrile function, and the amino alcohol (Scheme 15.12). 

In the last few years, an increasing interest in the elaboration of new NHC-Pt families of complexes has arisen. This includes Pt-oxazoline/NHC complexes, combining the heterocyclic ligand moiety as Al-substituent of NHC unit, or mixed Pt NHC/phosphine complexes developed by Rourke (Figure 10.4). The Cavell group described a l,3-diazepan-2-ylidene carbene and its coordination with Pt . On the other hand, Steinborn reported the synthesis and the characterization of Pt and Pt complexes with monodentate N,N-, N,0- or... 

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