Asymmetrische Hydrierung von (Z)‐α‐(Acetylamino)‐zimtsäure mit einem Rh/norphos‐Katalysator

Abstract

Ein verallgemeinerungsfähiges Verfahren zur Herstellung reiner Enantiomere chelatbildender Phosphane beruht auf der überraschend einfachen Racematspaltung der entsprechenden Phosphanoxide – hier (±)‐norphos O – mit L‐(−)‐Dibenzoylweinsäure. (+)‐ und (−)‐norphosO (nach zwei Trennschritten optisch rein) lassen sich mit SiHCl3 zu (+)‐ bzw. (−)‐norphos reduzieren, die mit Rh‐Verbindungen wertvolle Katalysatoren zur asymmetrischen Hydrierung bilden.

The Synthesis of Chiral Phosphorus Ligands for use in Homogeneous Metal Catalysis

“…[32] Owing to the high potential, several attempts have been made to find avenues to related www.chemcatchem.org structures. [33,34] In the first step, dichloroacetylene was converted into the corresponding diethoxy phosphorylated alkine. Now Salzer and Severins have patented a pathway based on the formation of the bridging scaffold through a cycloaddition reaction, as exemplarily depicted in Scheme 7.…”

“…Now Salzer and Severins have patented a pathway based on the formation of the bridging scaffold through a cycloaddition reaction, as exemplarily depicted in Scheme 7. [33,34] In the first step, dichloroacetylene was converted into the corresponding diethoxy phosphorylated alkine. Subsequent Diels-Alder-reaction with cyclopentadiene affords a norbornadiene skeleton.…”

Enantioselective Catalysis; 130: Optically Active Expanded Ligands Based on the trans-1,2-Substituted Cyclopentane Skeleton

“…For (R,R)-21a and (S,S)-21b 60-80% ee were achieved in several experiments, but only 23% ee for dpcp, 8 and less than 5% ee for diop 20 and norphos. 21 Only small amounts of water were used in the system (aqueous slurry of substrate) in order to assure complete hydrogenation. 9…”

Homo‐ and Cross‐Olefin Metathesis Coupling of Vinylphosphane Oxides and Electron‐Poor Alkenes: Access to P‐Stereogenic Dienophiles

“…trans-1,2-Bis(diphenylphosphanyl)ethene dioxide (7, R 1 ¼ R 2 ¼ Ph) was successfully used for the preparation of NORPHOS (3), [25] a highly active ligand possessing chirality centers in the rigid carbocyclic skeleton. Recently, intermolecular olefin cross metathesis and intramolecular ring-closing metathesis were applied for preparation of functionalized phosphorus compounds including allyl and vinyl phosphonates, [46] allylphosphane oxides, [47] and allylphosphane-boranes.…”

“…[22] Common optically active phosphane ligands developed in the 1970s and 1980s in this context are DIOP 1, [23] CHIRA-PHOS 2, [24] NORPHOS 3, [25] and BINAP 4, [26] which Scheme 1. Selected chiral diphosphane ligands for asymmetric catalysis.…”