Yttrium catalysts

Alkenes and alkynes can also add to each other to give cyclic products in other ways (see 15-61 and 15-63). The first exclusive exo-dig carbocyclization was reported using HfCU as a catalyst. Alkynes also add to alkenes for form rings in the presence of a palladium catalyst or a zirconium catalyst. " Carbocyclization of an alkene unit to another alkene unit was reported using an yttrium catalyst and alkenes add to alkynes to give cyclic compounds with titanium catalysts. ... 

Intermolecular Hydrosilylation of Internal Alkynes 10.17.3.5.1 Yttrium catalysts for regiocontrol based on sterics... 

Ajellal N, Bouyahyi M, Amgoune A, Thomas CM, Bondon A, Pillin I, Grohens Y, Carpentier J-F (2009) Syndiotactic-eirriched Poly(3-hydroxybutyrate)s via stereoselective ring-opening polymerization of racemic (3-butyrolactone with discrete yttrium catalysts. Macromolecules 42 987-993... 

Mass-spectrometer date of the hydrogenated carbon nanotubes we have published in (Shulga et al. 2004). These nanotubes for the gas mass-spectrometry were synthesized by the electric-arc method using a nickel-yttrium catalyst. To remove amorphous carbon and the metal catalyst, the primary products containing 10-15 wt% of carbon SWNTs were purified by repeated oxidation in air at temperatures... 

The first basic asymmetric catalysts of type A were prepared from LnCl3 (Ln = Y or La) and enantiopure bidentate diol derivatives such as 164 under the conditions outlined in Figure 3. Although the structures of the type A catalytic species were still open to conjecture, they nonetheless proved effective for catalytic asymmetric reactions. Thus treatment of 14 with the yttrium catalyst of type A in THF at -52 °C for 6 days gave a 60% yield of 15a with 52% ee.5 However, it was shown that the enantiomeric purity of isolated 15a decreased when further exposed to the type A catalyst at -30 °C, suggesting that the product had a tendency to undergo a retro aldol reaction. 

Chiral salen yttrium complexes were also examined in the ring-opening polymerization of LA (R-3, (S,S)-7, Figure 25.8). Although the yttrium catalyst R-3 showed higher kinetic activity (faster polymerization rate) than A1 catalyst R-2, unlike R-2, it produced atactic PLA from meso-LA. Similarly, atactic PLA was formed from rac-LA by the (5,5-salen) yttrium catalyst (S,S)-7." " ... 

Primary and secondary alcohols reacted with vinyl or isopropenyl acetate at room temperature in he presence of a catalytic amount (0.05-1 mol%) ofY5(OTr)i30 to give the corresponding esters (Scheme 12.84) [183]. In selected cases, the yttrium catalyst promoted selective O-acylation of amino alcohols without the formation of an amide. Enol esters also reacted with a-amino acid esters in the absence of a catalyst at room temperature to give the corresponding amides. 

The formation of seven-membered rings constitutes another significant challenge for post-metallocene catalysts, but can be accomplished utilizing the bis(amidate) yttrium catalyst 10 (1) [94]. 

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