Date of Award
Summer 2011
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Yi, Chae S.
Second Advisor
Donaldson, William A.
Third Advisor
Gardinier, James R.
Abstract
Transition metal-catalyzed C-C bond forming reactions involving C-H bond activation have been shown to be effective methods for functionalization of unreactive compounds. Since Murai's pioneering work on ruthenium-catalyzed regioselective arene-to-alkene coupling reactions, a number of well-defined, late transition metal catalysts have been shown to mediate regioseletive C-C bond forming reaction involving C-H bond activation. Recently, late transition metal complexes have also been found to catalyze the regioselective coupling reaction of nitrogen containing compounds with alkenes as well as sp3 bond insertions and oxidative coupling reaction of aimdes. The catalytic C-C bond forming reaction involving C-H bond activation would provide simple and atom economic pathways for making functionalized molecules. Although there are many examples of stoichiometric reaction of aromatic C-H bond activation with transition metal compounds, catalytic C-H bond activation reactions via catalytic system have been rarely employed in organic synthesis.
An efficient catalytic conjugate addition reaction protocol has been developed for the synthesis of tetrasubstituted olefin products. The cationic ruthenium-hydride complex was found to be an effective catalyst for coupling reaction with á,â-unsaturated carbonyl compounds and simple alkenes. The kinetic and spectroscopic data are consistent with three different mechanistic pathways depending on substrate employed. The reaction of an á,â-unsaturated carbonyl compounds with simple olefins predominantly gave the tetrasubstituted olefin products. The mechanistic studies suggest that the olefin insertion into an á,â-unsaturated carbonyl substrate is the rate-limiting step for conjugate addition reaction. On the other hand, the coupling reaction of á-methyl á,â-unsaturated cinnamide with aromatic alkenes gave oxidative coupling products. The kinetic and spectroscopic studies support the different mechanistic pathway, which involves the rate-limiting vinyl C-H activation step, in comparison with the conjugate addition reaction. This synthetic methodology promises to provide a straightforward route to the valuable organic compounds such as tetrasubstituted olefins which are difficult to synthesize by using traditional synthetic methods.