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Synthesis 2006(13): 2191-2200  
DOI: 10.1055/s-2006-942429
PAPER
© Georg Thieme Verlag Stuttgart · New York

Functional-Group Attachment and Interconversion at a Chiral [3]Ferrocenophane Framework

Christian Nilewski, Markus Neumann, Ludger Tebben, Roland Fröhlich, Gerald Kehr, Gerhard Erker*
Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
Fax: +49(251)8336503; e-Mail: erker@uni-muenster.de;
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Publication History

Received 16 May 2006
Publication Date:
24 June 2006 (online)

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Abstract

Mannich condensation of 1,1′-diacetylferrocene with dimethylamine followed by catalytic hydrogenation gives the chiral α-dimethylamino[3]ferrocenophane. Both enantiomers are available by resolution. Directed ortho-lithiation/iodination yields the ortho-iodo-α-dimethylamino[3]ferrocenophane derivative, whose treatment with acetic anhydride and copper(I) oxide yielded the mono- and diacetoxy-functionalized derivatives. The ortho-phosphorylated α-dimethylamino systems (-PPh2, -PCy2) underwent exchange of the directing NMe2 group with NH2 by means of an ammonolysis reaction of the corresponding α-chloride derivatives, which in turn were obtained by treatment of the α-dimethylamino compounds with methylchloroformate. Starting from α-dimethyl­amino[3]ferrocenophane, the sequence of directed ortho-lithiation (t-BuLi), treatment with p-tosyl azide/sodium pyrophosphate (to yield the ortho-azido[3]ferrocenophane derivative) followed by catalytic hydrogenation gave the ortho-amino and α-dimethylamino[3]ferrocenophane derivatives. The potential use of some of the chelate ferrocenophane ligands in Ru-catalyzed asymmetric hydrogenations was investigated. Seven of the newly synthesized compounds were characterized by X-ray diffraction.

Key words

ferrocene - chelate ligand - amino group - P,N-ligand - asymmetric hydrogenation - catalysis