In this project a new method for ruthenium catalyzed dehydrogenative coupling of alcohols and amines to form imines is presented.
Imines are common ligands in coordination chemistry, in other words they are important organic chemistry tools. In this thesis, a method for direct (one step) synthesis of imines from alcohols and amines is presented. The method provides quick and extended access to structurally diverse and synthetically important imines.
In a separate, second part of the thesis novel synthetic methods for assembling oligosaccharides are presented. Such methods are essential tools for the emerging fields of glycobiology and glyconomics.
Both projects have metal-mediated couplings of primary alcohols with amines and carbohydrates as a common denominator.
Synthesis of imines via dehydrogenative coupling of alcohols and amines has recently become of great interest mainly for its broad applicability and environmental friendliness.
In 2008, Madsen and co-workers performed the amide synthesis with an in situ generated Ru-NHC catalyst. The present project builds on this work.
In this project a new method for the dehydrogenative coupling of alcohols and amines to form imines is presented. The reaction is catalyzed by the ruthenium N-heterocyclic carbene complex [RuCl2(IiPr) (p-cymene)] in the presence of the ligand DABCO and molecular sieves. The method can be applied to a variety of primary alcohols and amines and can be combined with a subsequent addition reaction.
The second, separate project is focused on tin mediated regioselective 6-O-glycosylations of unprotected glycopyranosides acceptors.The development of efficient synthetic methods for assembling oligosaccharides has become an essential tool for the emerging fields of glycobiology and glycomics.
A key area in glycobiology is cell surface molecules. These play a key role in numerous biological processes such as cell recognition events including cell adhesion, host-pathogen interactions, cancer progression, spermatogenesis, and development of the nervous system. The growing interest in these molecules has increased the demand for structurally defined oligosaccharides, as these constitute a major class of cell surface molecules.
Even though a vast number of synthetic methods is available, the assembly of complex glycans is still an intricate process and the development of easier and more efficient procedures remains a primary goal. The major constraint of oligosaccharide synthesis is the extensive use of protecting groups. Thus, approaches to reduce the number of steps connected to chemical synthesis are highly important.
In this thesis thioglycosides deriving from D-glucose, D-galactose, and D-mannose were coupled with different bromide donors to afford the corresponding 1-6 linked disaccharides in good to moderate yields. Furthermore, it has been shown that these disaccharides can act as glycosyl donors for subsequent tin mediated glycosylation reactions.