Enantioselektive Katalyse, 121. Mitt. [1]: Chirale Phosphanliganden mit zusätzlichen Sauerstoffunktionalitäten

Abstract

Enantioselective Catalysis CXXI [1]: Chiral Phosphane Ligands with Additional Oxygen FunctionalitiesSummary. New optically active phosphane ligands with additional ether and hydroxy functionalities were synthesied and used as sources of enantio-selectivity in the Ni-catalyzed cross coupling reaction of 1-phenylethyl Grignard and vinylbromide and in the Pd-catalyzed allylation of 1,5-dimethylbarbituric acid with allyl acetate.

Highly Enantioselective Rhodium‐Catalyzed Hydrogenation of 2‐(2‐Methoxy‐2‐oxoethyl)acrylic Acid − A Convenient Access of Enantiomerically Pure Isoprenoid Building Blocks

“…The requisite alcohol (S)-10 was prepared from (S)-mandelic acid. [21] Reaction of (S)-10 at Ϫ78°C with phosphorous chloride 9 [22] (1.1 equivalents) in toluene in the presence of triethylamine gave crude ligand L2 in excellent yield. Purity of ligand L2, assessed by 31 P NMR (singlet at δ ϭ 151.54 ppm), was ca.…”

Enantioselective Catalytic Transformations of Barbituric Acid Derivatives

“…Despite great synthetic advances in this field of research, the use of diastereoselective sequences or separation techniques (crystallization or chromatography) of racemic mixtures were required for the elaboration of enantiopure architectures of chiral bioactive compounds as depicted in Figure 1 [19]. At the end of the 1990s, the pioneering research of Brunner's group, on the palladium-catalyzed enantioselective alkylation of barbituric acid derivatives have shed light on the potential of this starting material in asymmetric synthesis while pointing out challenges, which have to be overcome with this unique architecture [20][21][22][23]. This review intends to cover the literature dealing with the enantioselective catalytic transformations of barbituric acid derivatives, an exercise which is unprecedented to the best of our knowledge.…”

“…During subsequent investigations, this group of researchers took advantage of the readily available phosphine imines like 17, easily synthesized from the corresponding aldehyde with suitable chiral amines (Scheme 2). Then, 134 various ligands were evaluated in this enantioselective allylation process of 13 [20,23]. The novel phosphine ligand 17 allowed to improve the ee up to 34% for product 14, and another side-product, 16, which originated from the double allylation reaction was observed in these conditions.…”