Divalent Samarium Triflate Mediated Stereoselective Pinacol Coupling of Planar Chiral Phosphanyl and Phosphoryl Ferrocenecarbaldehyde

✍ Scribed by Shin-ichi Fukuzawa; Ichiro Oura; Kenta Shimizu; Minoru Kato; Ken-ichi Ogata

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 249 KB
• Volume: 2009
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200801138

✦ Synopsis

Abstract

The pinacol coupling reaction of (Rp)‐2‐diphenylphosphanyl ferrocenecarbaldehyde (1) was smoothly mediated by divalent samarium triflate to give (R,R)‐diol 2a predominantly, whereas the use of samarium(II) iodide resulted in low selectivity as described in the previous literature. In contrast, the coupling reaction of (Rp)‐2‐diphenylphosphoryl ferrocenecarbaldehyde (3) with Sm(OTf)~2~ gave the (S,S)‐diol as the major isomer, which was the opposite stereochemistry of that obtained in the reaction with 1. The rhodium complexes of diphosphanes 2a were good catalysts for the asymmetric hydrogenation of α‐acetamidocinnamic acid, and the product was obtained quantitatively with up to 92 % ee. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)