| Catalysis of the (2+3) reaction of nitrones with electron rich olefins by the Lewis acid {dollar}rm Cpsb2Ti(OTf)sb2{dollar} was investigated. The reaction was strongly catalyzed by protons resulting from hydrolysis of the catalyst, however, the strong base Proton-Sponge{dollar}spcircler{dollar} was an effective inhibitor of the proton catalysis. Catalysis by titanium was demonstrated, however the rates of reaction were modest, and depended on the degree of substitution of the olefin, and the structure of the nitrone. The structure of the catalytic species was investigated. Both mono and bis nitrone complexes of {dollar}rm Cpsb2Ti(OTf)sb2{dollar} were characterized in solution, and the bis complex was characterized by X-ray crystallography. Low levels of asymmetric induction were found with a chiral catalyst, however the steric bulk of the catalyst severely inhibited the reaction rates.; Catalysis of the carbonyl-ene reaction by an air and water stable, structurally characterized, cationic ruthenium complex (3.4) was demonstrated. Low loadings (2 mol%) were sufficient to allow efficient turnover at 50{dollar}spcirc{dollar}C for the reaction of 1,1{dollar}spprime{dollar}-disubstituted olefins with electron deficient aromatic olefins and diethyl ketomalonate. A stepwise mechanism involving a dipolar intermediate was proposed for the reaction.; The mild Lewis acids Eu(hfc){dollar}sb3{dollar} and (Zn(facac){dollar}rmsb2(Hsb2O)sb2{dollar}) were shown to catalyze the Mukaiyama reaction between silyl ketene acetals and aldehydes. The mechanism of the reaction was studied, and oxetanes resulting from a reversible (2+2) reaction were observed and characterized. A new mechanism for the reaction was proposed, taking into account the formation of the oxetanes.; Finally, biaryl strapped bis(2-tetrahydroindenyl) complexes of titanium and zirconium were prepared. The complexes were prepared from bis(2-indene) precursors, and formed single C{dollar}sb2{dollar}-symmetrical isomers. Homochiral complexes were prepared from a homochiral precursor (S-5.5). Two of the titanium complexes were characterized by X-ray crystallography. The titanium complexes were investigated as asymmetric catalysts for the hydrogenation of olefins. Low turnover rates and ee's were found in a small survey. The asymmetric hydrosilylation of ketones was also investigated, however no ee's could be observed. |
