On the Role of Planar Chirality in Asymmetric Catalysis:  A Study toward Appropriate Ferrocene Ligands for Diethylzinc Additions

• Published in: Journal of organic chemistry Vol. 63; no. 22; pp. 7860 - 7867
• Main Authors: Bolm, Carsten, Muñiz-Fernández, Kilian, Seger, Andreas, Raabe, Gerhard, Günther, Kurt
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 30.10.1998; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Physical Sciences; Science & Technology; ORGANOZINC REAGENTS; EFFICIENT CATALYST; KINETIC RESOLUTION; PHOSPHINE HYBRID LIGAND; ALDEHYDES; ENANTIOSELECTIVE ADDITION; DIPHENYLPHOSPHINO(OXAZOLINYL)FERROCENE LIGANDS; GOLD(I)-CATALYZED ALDOL REACTION; GRIGNARD-REAGENTS; METAL-COMPLEXES
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo981098r

Employing a directed ortho-metalation route, chiral ferrocene-based hydroxyloxazolines have been synthesized, and their capability to serve as bidentate ligand precursors in the diethylzinc addition to benzaldehyde has been investigated. On the basis of the X-ray crystal structures of two ferrocenes, (S,R p)-6 and (S,S p)-10, it became possible to determine the general importance of the element of planar chirality for diastereomeric ferrocene complexes in this process. Comparison of the assumed transition states revealed a preferential catalyst conformation which led to the design of an adequate arene compound [(S)-20] that displayed catalytic activity similar to that of (S,R p)-6.