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New Catalysts for Base-Catalysed Hydroamination Reactions of Olefins

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New Catalysts for Base-Catalysed Hydroamination Reactions of Olefins New Catalysts for Base-Catalysed Hydroamination Reactions of Olefins Den Naturwissenschaftlichen Fakultäten der Friedrich-Alexander-Universität Erlangen-Nürnberg zur Erlangung des Doktorgrades vorgelegt von Patricia Horrillo Martínez aus Tudela de Navarra, Spanien Als Dissertation genehmigt von den Naturwissenschaftlichen Fakultäten der Universität Erlangen-Nürnberg Tag der mündlichen Prüfung: 18.07.2008 Vorsitzender der Promotionskommission: Prof. Dr. E. Bänsch Erstberichterstatter: Assist. Prof. Dr. K. C. Hultzsch Zweitberichterstatter: Prof. Dr. H. Gröger a mis Padres y Achim Die vorliegende Arbeit wurde am Institut für Organische Chemie der Friedrich-Alexander- Universität Erlangen-Nürnberg in der Zeit von Oktober 2003 bis September 2007 unter Anleitung von Priv. Doz. Dr. Kai C. Hultzsch angefertigt. Ich danke Dr. Kai C. Hultzsch für den wissenschaftlichen Anstoß, das stetige Interesse an dieser Arbeit sowie die wertvolle Hilfe bei der Erstellung dieses Manuskripts. Auch danke ich Prof. John A. Gladysz für die Möglichkeit in seiner Gruppe promovieren zu können und für die interessante Diskussionen. Den Angestellten des Organischen Instituts möchte ich für Ihre Hilfe danken: Dr. Frank Hampel und Wolfgang Donaubauer (Röntgenstrukturanalyse), Wilfried Schätzke, Christian Placht und besonderes Prof. Walter Bauer (NMR –Spektroskopie), Wolfgang Donaubauer und Margarete Dziallach (mindestens tausend mal haben Sie Massenspektren für mich gemessen), Eva Hergenröder (Elementaranalyse), Hannelore Oschmann und Robert Panzer (Chemikalien), Stefan Fronius und Bahram Saberi (Glasbläserei), Erwin Schreier und Eberhard Ruprecht (Mechanische Werkstatt), Reinhard Wolff und Holger Wohlfahrt (ehemaliger und neuer Hausmeister). Mein besonderer Dank geht auch an Dr. Frank Hampel, Christiane Brandl-Rittel und Pamela Engerer für die freundliche Hilfe mit administrativen Dingen. Ich danke meinen Laborkollegen Inka, Boyan, Alexander und vor allem Denis für die nette Atmosphäre und die gute Zusammenarbeit. Dem gesamten Arbeitskreis Gladysz (ehemalige und gegenwärtige Mitarbeiter) danke ich für die wunderbaren Jahre in Erlangen. Ihr werdet für immer in meinem Herzen bleiben. Ich danke auch den Fußballspielern des Instituts: Der Dienstag war immer etwas Besonderes. Mein herzlicher Dank gilt meinen Freunden in Deutschland (Patri 1, Verona, Laura, Elena, Yolanda, Sergio, Saul, Jose P., Ana, Carolina, Anne-So, Patrick) und in Spanien (Eva und Pere, Sonia, Chloe, Roser und Joan, Salut, Maria, Isabel, Anna, Adrià, Jose A.) für die moralische Unterstützung. Ganz besonders danke ich meinen Eltern, meiner Schwester und Achim für ihre bedingungslose Unterstützung. Zusammenfassung Die vorliegende Arbeit umfasst die Synthese von neuartigen, Prolin-modifizierten, chiralen Binaphthyl-Komplexen ausgewählter Hauptgruppen- (Li, Mg, Zn) und Seltenerdmetallen (Y, La), sowie deren Anwendung in der intramolekularen Hydroaminierung von Aminoalkenen, Aminodialkenen und Aminoalkinen. Hydroaminierungen von Vinylaromaten mit primären und sekundären Aminen wurden unter Verwendung geringer Katalysatorbeladungen von [(TMEDA) Li{N(SiMe3)2}] (29) bis hinab zu 2 mol% untersucht. Bei 120 °C laufen diese Reaktionen, ohne Zusatz von Lösungsmitteln, zügig und selektiv zu den anti-Markovnikov Produkten ab und ermöglichen deren Isolierung in 23-96% Ausbeute. Im Falle elektronenarmer p-Chlorstyrole oder sekundärer, zyklischer Amine, wie zum Beispiel Pyrrolidin, Piperidin oder Morpholin, kann bereits bei 25 °C langsame Hydroaminierungsaktivität festgestellt werden. Primäre Amine jedoch können einer nachfolgenden, zweiten Hydroaminierung unterliegen und somit auch zu tertiären Aminen führen. Unter Verwendung eines Amin- Überschusses war es hierbei möglich die Selektivität bezüglich des mono-hydroaminierten Produkts gegenüber dem tertiären Amin zu erhöhen. Des Weiteren wurde die intermolekulare Hydroaminierung von Vinylaromaten mit zahlreichen primären und sekundären Aminen in Anwesenheit einfacher Lithium- und Kaliumamide untersucht. Im Vergleich zu [Li{N(SiMe3)2}], konnte für [K{N(SiMe3)2}] eine höhere katalytische Aktivität bei verringerter Selektivität festgestellt werden, die sich in der Bildung unerwünschter Nebenprodukte durch α-C-H-Aktivierung äußerte. 2mol%[Li{N(SiMe3)2}] 2mol%Additiv R' Ar N Ar + HN R'R'' Ar R'' + N 25-120 °C Ar R'' R' = H Die durchgeführten Studien zur Reaktionskinetik, sowie deren theoretische Berechnung stehen im Einklang mit dem postulierten basen-katalysierten Reaktionsmechanismus. Die Reaktion primärer Amine durchläuft zwei aufeinander folgende Additions-schritte, wobei der erste signifikant schneller ablaufen muss. Der anfängliche Hydroaminierungsschritt verläuft kinetisch nach erster Ordnung bezüglich der Konzentration von Styrol und Benzylamin, jedoch nach unerwarteter nullter Ordnung bezüglich der Katalysatorkonzentration. Vorläufige Versuche deuten an, dass [(TMEDA)Li(NHCH2Ph)] eine deutlich höhere katalytische Aktivität aufweist, wodurch eine Reaktionsführung bei Raumtemperatur ermöglich wird. Die Reaktion verläuft in diesem System nach einer Kinetik erster Ordnung in Bezug auf die Konzentration an Styrol, Benzylamin und Katalysator. Die ermittelte Kinetik erster Ordnung bezüglich der Katalysatorkonzentration unterstützt den angenommenen Katalysezyklus der Lithium- Benzylamid-katalysierten Umsetzung. Die L-Prolin modifizierten, axial-chiralen Tetramin-Verbindungen (S,S,S)-DABN(MeProlin)2 ((S,S,S)-40) und (R,S,S)-DABN(MeProlin)2 ((R,S,S)-41) konnten in moderaten bis guten Ausbeuten (44-88%) hergestellt werden. Nachfolgende Lithiierung in Hexan führt zu den diastereomeren Di-Lithium Salzen [Li2{(S,S,S)-DABN (MeProline)2}]2 ((S,S,S)-47) und [Li2{(R,S,S)-DABN(MeProline)2}] ((R,S,S)-49), wobei ersteres auch durch Röntgenstrukturanalyse nachgewiesen werden konnte. Durch Modifikation des Ligandgerüstes sind auch die Komplexverbindungen [Li2{(R)-DABN (SitBuMe2)2}(THF)2] ((R)-50), Lithium (S)-1-Methyl-2-[N-1-naphthylamino)methyl]- pyrrolidin ((S)-51) und Di-lithium-(N,N-DiMeProlin)-2,2’-diamino-4,4’-di-tert-butyl- biphenyl ((S,S)-52) in 70%, 86% beziehungsweise 57% Ausbeute zugänglich. Eine Variation des Zentralmetalls führt zur Isolierung der bimetallischen Magnesium und Zink Komplexe [Mg2{(S,S,S)-DABN(MeProlin)2}{Bu}2] ((S,S,S)-53), [Mg2{(R,S,S)-DABN (MeProlin)2}{Bu}2] ((R,S,S)-54), [Zn2{(S,S,S)-DABN(MeProlin)2}{Et}2] ((S,S,S)-55) und [Zn2{(R,S,S)-DABN(MeProlin)2}{Et}2] ((R,S,S)-56) in 62-76% Ausbeute. N N Me Me NH NH NH Me NH Me N N (S,S,S)-40 (R,S,S)-41 Mit dem Lithium-Komplex (S,S,S)-47 wurde das erste Beispiel eines Lithium- Katalysators für die asymmetrische Hydroaminierung/Zyklisierung von Aminoalkenen gefunden. Für einige Aminoalkene zeigt dieser Katalysator vergleichbare Aktivitäten mit jenen, die für die Lanthanoid-basierten Systeme und die Katalysatoren mit Übergangsmetallen der vierten Gruppe gefunden wurden, wobei die Lithium-basierte viii Verbindung Enantioselektivitäten von bis zu 85% ee in der Zyklisierung von C-(1-Allyl- cyclohexyl)-methylamin (S4) erzielen konnte. Eine niedrigere Reaktivität und Selektivität der Katalysatoren (R)-50, (S)-51 und (S,S)-52 weist darauf hin, dass sowohl die chirale Diaminobinaphthyleinheit, als auch die L-Prolin-Gruppen entscheidenden Einfluss auf die Leistungsfähigkeit des Katalysators ausüben. H N 4mol%(S,S,S)-47 NH2 toluol-d8, 9h,0°C S4 P4 91% (84% ee) Weiterhin erwiesen sich die Magnesium und Zink Komplexe (S,S,S)-53, (R,S,S)-54, (S,S,S)-55, und (R,S,S)-56 als aktive Katalysatoren in der intramolekularen Hydroaminierung/Zyklisierung. Im Speziellen zeigte der Magnesium Komplex (S,S,S)-53 eine ausgesprochen hohe katalytische Aktivität für die Zyklisierungsreaktion von 2,2-Diphenyl-1-aminopent-4-en (S3), wobei im Allgemeinen niedrige Enantioselektivitäten (0-29% ee) beobachtet wurden. Kinetische Untersuchungen zur (S,S,S)-47-katalysierten Hydroaminierung/ Zyklisierung von S4 legten eine Abhängigkeit nach erster Ordnung bezüglich der Substrat- und Katalysatorkonzentration offen. Die Aktivierungsparameter für den tief- und hochliegenden Übergangszustand zu den Pyrrolidin-Produkten (S)-P4 und (R)-P4 wurde ermittelt (ΔH(S)≠ = 54(4) kJ mol-1, ΔS(S)≠ = -129(14) J K-1 mol-1 und ΔH(R)≠ = 65(5) kJ mol-1, ΔS(S)≠ = -109(17) J K-1 mol-1). Mit β-substituierten Aminoalkenen konnte die kinetische Racematspaltung unter Verwendung von (S,S,S)-47 durchgeführt werden, was im Falle der α-substituierten Analoga nur in sterisch stark abgeschirmten Systemen gelang. Die Lanthanoid Komplexe [Ln{(S,S,S)-DABN(MeProlin)2}{N(SiMe3)2}] [Ln = Y ((S,S,S)-79), La ((S,S,S)-80)] wurden in situ im NMR-Maßstab hergestellt und im Hinblick auf ihre katalytische Aktivität in Hydroaminierungs/Zyklisierungs-Reaktionen untersucht. Weiterhin wurden die kationischen Zirconium Komplexe (S,S,S)-81 und (R,S,S)-82, welche sich von den entsprechenden L-Prolin derivatisierten Diaminobinaphthyl-Liganden ableiten, in 85% beziehungsweise 99% Ausbeute synthetisiert. Die neutralen Komplexe der vierten Gruppe [M{(R)-DABN(py)2}(NMe2)2] ix (M = Ti ((R)-83), Zr ((R)-85)) konnten erhalten und NMR-spektroskopisch charakterisiert werden. Die Lanthanoid Komplexe (S,S,S)-79 und (S,S,S)-80 erwiesen sich als aktive Katalysatoren für eine Ringschlussreaktion des 2,2-Dimethyl-pent-4-enylamins (S1), wobei jedoch geringe Selektivitäten in Kauf genommen werden müssen (maximal 11% ee). Beide Katalysatoren ermöglichen auch die Umsetzung anderer Substrate zu den analogen Produkten. Um hohe Umsatzraten zu beobachten, werden hierfür allerdings lange Reaktionszeiten und in einigen
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