Development of transition metal-catalyzed redox allylation reactions and a rhodium-catalyzed stereospecific oxazolidine synthesis

The allylation reactions of electrophiles has broad utility in the synthesis of small organic molecules. The development of methodologies that address this bond construction has been an active area of research over the past few decades. However, these methods have limitations. Many of these methodologies utilize expensive reagents, complex allylmetal species that need synthesized, and stoichiometric amounts of a metal. The development of transformations that are catalytic in metal that utilize allylic alcohols or allylic halides, such as redox allylation, is a challenging problem that is the current focus of much current research.;We sought to address this challenge by developing new nucleophilic allylmetal species as catalytic reaction intermediates. Nucleophilic allylpalladium complexes containing bidentate NHC ligands were developed as catalysts to allylate aldehydes. The reaction was first developed using stoichiometric amounts of palladium to study the key bond-forming step. Using the knowledge gained during these experiments, a redox allylation reaction was developed, using a palladium catalyst and hexamethyldisilane as a reductant. This allylation reaction of imines was found to be amenable to a three-component process in which aldehydes are used as starting materials and undergo a condensation reaction with p-anisidine to form the imines in situ. A rhodium-catalyzed redox allylation reaction of ketones was also realized. During the development of this rhodium-catalyzed reaction, a stereospecific oxazolidine synthesis from vinyl epoxide and imines was discovered.