Asymmetrie hydrogenation of imines and enamines using phosphoramidite ligands

Promotie: mw. N. Mrŝić, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen
Proefschrift: Asymmetrie hydrogenation of imines and enamines using phosphoramidite ligands
Promotor(s): prof.dr. J.G. de Vries, prof.dr. B.L. Feringa, prof.dr. A.J. Minnaard
Faculteit: Wiskunde en Natuurwetenschappen
Contact: Nataša Mršic, tel. 00 385 1372 2037, e-mail: n.mrsic@rug.nl

Asymmetrie hydrogenation of imines and enamines using phosphoramidite ligands

Asymmetric hydrogenation (AH) represents a versatile, clean and atom economic method for the preparation of enantiopure compounds. We were in particularly interested in the AH of heteroaromatic compounds such as quinolines, quinoxalines and indoles, due to the fact that chiral heterocyclic compounds are often found as part of the structures of pharmaceuticals and physiologically active compounds. In this thesis Nataša Mršic describes the AH of 2- and 2,6-substituted quinolines and quinoxalines catalyzed by iridium complexes of BINOL-derived phosphoramidites. Enantioselectivities of up to 89% and 96%, respectively, were obtained. Primary chiral amines were obtained via the asymmetric hydrogenation of N-aryl imines, followed by the subsequent deprotection of the secondary amines. Enantioselectivities up to >99% were obtained. We were also able to perform hydrogenation of indoles catalyzed by rhodium complexes with phosphoramidite ligands. Full conversions and enantioselectivities up to 74% were obtained in the hydrogenation of N-protected indoles. Finally, we developed a route to beta-amino acid derivatives via the AH of N-aryl beta-enamino acid esters. Full conversions and enantioselectivities of up to 70% were obtained using an Ir/phosphoramidite catalytic system. The products that are made by this technology are mostly used as building blocks for medicines and to a lesser extent also for agrochemicals and flavours and fragrances.