Nina Hermanns

Catalyzed Asymmetric Arylation Reactions

Addition and substitution reactions with carbon nucleophiles are fundamental processes in organic synthesis, and the development of general catalytic asymmetric variants thereof is still a major challenge today. In contrast to enantioselective alkyl transfer reactions, the corresponding arylations have not yet reached a high level of maturity. The existing protocols are either of no general applicability or are limited in terms of selectivity. This article summarizes established routes for catalytic asymmetric aryl transfer together with the latest developments in this area. The scope and limitations of this reaction are discussed.

Katalysierte asymmetrische Arylierungen

Additions- und Substitutionsreaktionen mit Kohlenstoffnucleophilen sind grundlegende Prozesse der organischen Synthese, und die Entwicklung von breit anwendbaren asymmetrischen Varianten ist heutzutage noch immer eine grose Herausforderung. Im Unterschied zu enantioselektiven Alkyltransferreaktionen sind die entsprechenden Arylierungen bei weitem noch nicht ausgereift, und die bekannten Verfahren zeichnen sich entweder durch eine begrenzte Anwendungsbreite oder eingeschrankte Selektivitaten aus. In dieser Ubersicht fassen wir die bestehenden Verfahren zu katalysierten enantioselektiven Arylubertragungen zusammen und stellen neuere Entwicklungen in diesem Bereich vor.

Synthesis of novel 1,1′-bis(oxazolinyl)metallocenes and their application in the asymmetric phenyl transfer from organozincs to aldehydes

Abstract Two novel C2-symmetric 1,1′-bis(oxazolinyl)metallocenes bearing two catalytic sites each have been employed in the asymmetric phenyl transfer from organozincs to aldehydes. Both, ferrocene (3) and ruthenocene (10) give very good yields and high enantioselectivities in the title reaction affording optically active diarylmethanols with up to 96% ee.

A novel ferrocenyl diselenide for the catalytic asymmetric aryl transfer to aldehydes

An oxazolinyl ferrocenyl diselenide was synthesised by directed ortho-metalation and used as catalyst precursor in the asymmetric addition of diethyl- and diphenylzinc to various aldehydes, yielding synthetically useful secondary alcohols, of which some are difficult to access using other catalytic methodologies. Enantioselectivities of up to 44% for the former and up to 85% for the latter transformations were obtained.

Polymer-supported ferrocenyl oxazolines for the catalyzed highly enantioselective phenyl transfer to aldehydes.

A new chiral MeO-PEG-supported ferrocenyl oxazoline was synthesized and successfully employed in the enantioselective phenyl transfer to aldehydes. The products were obtained in high yields and with excellent enantioselectivities (up to 97% ee). Furthermore, the recovery of the ferrocene was facile, and catalyst efficiency was maintained in subsequent reactions.