Νέοι οργανοκαταλύτες και εφαρμογές τους σε ασύμμετρους οργανικούς μετασχηματισμούς

Nowadays, organocatalysis constitutes the third pillar of asymmetric catalysis, alongside transition metal catalysis and biocatalysis. The definition of organocatalysis is the use of low molecular weight organic molecules as catalysts in organic transformations.The goals of this thesis were on one hand, to synthesize novel organocatalysts based on natural aminoacids and evaluate their activity in known asymmetric transformations, and on the other hand, to exploit organocatalysis in general in order to accomplish unprecedented asymmetric reactions.In the context of synthesizing novel organocatalysts, we synthesized primary amine-thioureas based on di-tert-butyl aspartate and a chiral 1,2-diamine and we studied their catalytic activity in the asymmetric Michael reaction between ketones and nitroalkenes or nitrodienes. Σhe primary amine-thiourea consisting of di-tert-butyl aspartate and (1R, 2R)-diphenylethylene-1,2-diamine, was found to be a very powerful organocatalyst exhibiting remarkable results in the asymmetric Michael addition of methyl ketones to nitroalkenes or nitrodienes. The aforementioned organocatalyst was employed in the key-step of the asymmetric synthesis of the commercially available drug Baclofen.In addition, organocatalysts known in the literature were employed in order to develop unprecedented asymmetric transformations, such as the domino Michael-Henry reaction between 1,4-cyclohexanedione and nitroalkenes and the asymmetric Mannich addition of 2-chloro-1,3-dicarbonyl compounds or nitroalkanes to oxindole derived ketimines.Furthermore, a segment of this thesis focused on the synthesis of proline derivatives properly modified for immobilization on carbon nanotubes, in order to evaluate their catalytic activity in asymmetric aldol reactions.