Grubbs ruthenium catalysts Subject

Representatives of the bridged sulfone system 70 have been subjected to ruthenium catalysed ring-closing metathesis reactions (Grubbs catalyst) and shown to afford, in low yields, a few selected cyclic dimers and trimers, of all the possibilities available. The diastereoselectivities observed were rationalised in terms of kinetic control involved with internal ruthenium/sulfonyl oxygen coordination . 

This facile solution for catalyst immobilisation follows a more complex approach reported by Mayr et al. [246], This research group attached the imidazolium salt to a nor-bomene unit that was then subjected to a ring opening metathesis polymerisation (ROMP) reaction to form the polymeric NHC precursor (see Figure 4.77). The ROMP reaction had to be carried out with a molybdenum based Schrock catalyst because the ruthenium based Grubbs catalyst did not provide an endgroup that could be quantitatively capped with a suitable final endgroup. 

The metathesis reactions studied by the Tezuka group served two purposes, either they were used to analyze complex reaction mixtures, or they served as ring closing step. An example for an analytical application is illustrated in Formula 13.10. The reaction mixture consisting of two isomers (c) and (d) was subjected to metathesis with a ruthenium-based Grubbs catalyst [45]. Whereas, (c)... 

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