Gezielte Zugänge zu neuartigen lithiierten (Aminomethyl)ferrocenen in Hinblick auf planarchirale Katalysatoren
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Date
2018
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Abstract
(Aminomethyl)ferrocene stellen eine wichtige Verbindungsklasse in Hinblick auf neuartige chirale Liganden dar und haben ihr chemisches Potential bei weitem noch nicht ausgeschöpft. Als Resultat der vorliegenden Arbeit können abhängig von Reaktionsbedingungen und zuvor eingeführten Substituenten selektiv unterschiedliche Positionen an beiden Ferrocenylringen angesteuert werden.
Das enantiomerenreine ortho-lithiierte (Aminomethyl)ferrocen, zugänglich durch asymmetrische Metallierung, ist die Schlüsselverbindung zu allen weiteren chiralen Ligandensystemen. Nach der Umsetzung dieses lithiierten Ferrocens mit Disulfiden oder Thioether-Liganden konnte die zweite ortho-Position derivatisiert werden. Die Einführung des Dimethylmethoxysilyl-Substituenten in das (Aminomethyl)ferrocen bewirkte eine selektive Lithiierung in der 1‘ Position am unteren Ferrocenylring, welche hierdurch mit Sulfiden oder Phosphanen derivatisiert werden konnten. Basierend auf den chiralen 1‘ substituierten Verbindungen konnten weitere Derivatisierungen bspw. in der zweiten freien ortho Position durchgeführt werden.
Einen einmaligen Einblick in die Vorgänge der Metallierungsreaktionen geben die Molekülstrukturen lithiierter Intermediate, sowohl der 1‘ Lithiierung als auch der zweiten ortho-Lithiierung an diesen und an 1,1‘-trimethylsilylsubstituierten Ferrocenylderivaten.
Die neuartigen Liganden eignen sich zur Bildung von Metallkomplexen mit Kupfer-, Platin- oder Palladiumsalzen, welche bereits ihr Potential in der asymmetrischen Katalyse gezeigt haben.
(Aminomethyl)ferrocenes are very important compounds, which have a huge potential in the synthesis of novel chiral ligands. Dependend on the selected reaction conditions and the introduced substituents we could deprotonate both cyclopentadiene rings in different positions. The enantiopure ortho-lithiation (aminomethyl)ferrocene is the key access to a various number of ligands. After the successful lithiation and reaction with electrophiles, like disulfides or thioethers, the second deprotonation in ortho-position could be achieved. The use of dimethylmethoxysilane as electrophile enables a selective lithiation in 1’-position and a following derivatisation with sulfides or phosphines. Based on chiral 1’-substituted compounds a further metalation of the second ortho-position led to a new group of compounds. The successful X-ray investigations of the 1’-litiated intermediates as well as the second ortho-lithiated compounds of these 1’-substituted and 1,1’-trimethylsilyl substituted (aminomethyl)ferrocenes gave an incredible insight into metalation mechanisms, which can be used to solve a lot of synthetical problems. This novel enantiopure ligands were used to create a new group of potenatial chiral catalyst systems with different transtition metal salts as copper, platinum or palladium. First investigations in the catalytic activity of the chiral ligands provided auspicious results in asymmetric synthesis.
(Aminomethyl)ferrocenes are very important compounds, which have a huge potential in the synthesis of novel chiral ligands. Dependend on the selected reaction conditions and the introduced substituents we could deprotonate both cyclopentadiene rings in different positions. The enantiopure ortho-lithiation (aminomethyl)ferrocene is the key access to a various number of ligands. After the successful lithiation and reaction with electrophiles, like disulfides or thioethers, the second deprotonation in ortho-position could be achieved. The use of dimethylmethoxysilane as electrophile enables a selective lithiation in 1’-position and a following derivatisation with sulfides or phosphines. Based on chiral 1’-substituted compounds a further metalation of the second ortho-position led to a new group of compounds. The successful X-ray investigations of the 1’-litiated intermediates as well as the second ortho-lithiated compounds of these 1’-substituted and 1,1’-trimethylsilyl substituted (aminomethyl)ferrocenes gave an incredible insight into metalation mechanisms, which can be used to solve a lot of synthetical problems. This novel enantiopure ligands were used to create a new group of potenatial chiral catalyst systems with different transtition metal salts as copper, platinum or palladium. First investigations in the catalytic activity of the chiral ligands provided auspicious results in asymmetric synthesis.
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Metallorganik, Ferrocene, Katalyse, Planarchiral