Application of Transition Metal Catalysis to Small Molecule Synthesis
Over the past decade, transition metal catalysis has developed into a new field in organic synthesis, enabling numerous synthetic transformations that were previously not feasible. This thesis describes the application of both ruthenium and rhenium catalysis to the synthesis of several classes of s...
| Summary: | Over the past decade, transition metal catalysis has developed into a new field in organic synthesis, enabling numerous synthetic transformations that were previously not feasible. This thesis describes the application of both ruthenium and rhenium catalysis to the synthesis of several classes of small molecules. Ruthenium-catalyzed ring-opening cross-metathesis of five- through eight-membered ring cycloolefins was investigated for the synthesis of functionalized dienes (Chapter 1). Unsubstituted, trisubstituted, and allyl-substituted cycloolefins were studied. Regioselective reactions could be achieved with the use of unsymmetrical cycloolefins. Ruthenium-catalyzed cross-metathesis was explored for the synthesis of both di- and trisubstituted vinyl boronates (Chapter 2). These reactions proceeded efficiently for a wide variety of functionalized alkenes and generally exhibited high E-stereoselectivity. The resultant vinyl boronate products were stereoselectively converted into both Z-vinyl bromides and E-vinyl iodides. The rhenium-catalyzed 1,3-isomerization of allylic alcohols was employed in the synthesis of various allylic alcohols (Chapter 3). Two different strategies were developed to promote high product selectivity in these reactions: conjugated product synthesis and N,O-bis(trimethylsilyl)acetamide-promoted product trapping. These reactions enabled the synthesis of allylic alcohols with conjugated or non-conjugated, di- or trisubstituted, and electron-rich or electron-deficient alkene components. Partial chirality transfer was observed during the 1,3-isomerization of certain enantioenriched allylic alcohols. The fundamental reaction properties observed during these studies were all consistent with the operation of a mechanism involving a chair-like transition state, which contains a partially cationic allyl moiety, as the primary reaction pathway. |
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