Poly rare-earth metal catalysts

Rare earth metal triflates are recognized as a very efficient Lewis acid catalysts of several reactions including the aldol reaction, the Michael reaction, allylation, the Diels-Alder reaction, the Friedel-Crafts reaction, and glycosylation [110]. A polymer-sup-ported scandium catalyst has been developed and used for quinoline library synthesis (Sch. 8) [111], because lanthanide triflates were known to be effective in the synthesis of quinolines from A-arylimines [112,113]. This catalyst (103) was readily prepared from poly(acrylonitrile) 100 by chemical modification. A variety of combinations of aldehydes, amines, and olefins are possible in this reaction. Use of the polymer-supported catalyst has several advantages in quinoline library construction. 

The best results in obtaining high yields of c -1,4-poly isoprene are given by rare earth catalysts [252-257]. Similar to the polymerization of butadiene, three component catalysts (transition metal compound, Lewis acids, and alkyl aluminum) are used. It is necessary to have an excess of 4 to 10 times of the aluminum component. Most attractive... 

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