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The highly stereoselective synthesis of a chiral silylphospholane has been described, which can be advantageously used as a building block under base-free conditions for the construction of diphosphines related to DuPHOS. The utility of silylphospholane is shown in the synthesis of a new bisphospholane ligand 1 (MalPHOS), which is characterized by a maleic anhydride backbone. The ligand forms with Rh(I) a complex with a larger bite angle P-Rh-P than the analogue Me-DuPHOS complex. Both complexes have been tested in the asymmetric hydrogenation of unsaturated alpha- and beta-amino acid precursors of pharmaceutical relevance. In several cases, the new catalyst was superior in comparison to the Me-DuPHOS complex, in particular when (Z)-configured beta-acylamido acrylates were used as substrates.

The asymmetric synthesis of a range of axially chiral 2-arylpyridines by a cobalt-catalyzed [2 + 2 + 2] cycloaddition reaction is described. The use of a planar chiral (1-neomenthylindenyl)cobalt(COD) complex under photochemical conditions is the key for reacting the 1-naphthyldiynes with a range of differently functionalized nitriles, giving the enantiomeric atropoisomers with high chemical yields and enantiomeric excesses of up to 94% ee.

The palladium‐catalyzed CH activation and arylation of N‐methylpyrrole and N‐phenylpyrrole allowed a convenient synthesis of diarylpyrroles. The reactions were performed by using tetrabutylammonium acetate as an ionic solvent, which allowed for the application of a ligand‐free catalytic system by using simple palladium salts or polyvinylpyrrolidone‐stabilized palladium nanoparticles as the catalyst.

This contribution gives an overview of the synthesis of chiral -amino acids via asymmetric hydrogenation of the corresponding dehydroamino derivatives. Literature results are discussed regarding substrate synthesis and catalyst performance and how it is affected by substrate and catalyst structure as well as experimental parameters. A tentative mechanistic concept for the hydrogenation step is also presented. IntroductionEnantiomerically pure -amino acids and their derivatives not only exhibit broad biological activity but are also the building blocks for the synthesis of -peptides. The latter are characterized by a high enzymatic stability and show interesting three-dimensional structures. 1 The cyclization of -amino acids leads to the important family of the -lactams. Scheme 1 shows examples of pharmaceutically interesting structures containing a -aryl-substituted -amino acid as a common structural component. 2 Methods for the preparation of optically enriched -amino acids are predominantly based on stoichiometric reactions with chiral auxiliary agents and to a clearly smaller extent on stereoselective catalytic reactions. 2d,e,3 One of the most promising methodologies, also regarding industrial application, is the asymmetric hydrogenation of the appropriate -dehydroamino acid precursors catalyzed by homogeneous Rh or Ru complexes containing chiral phosphane ligands. In contrast to the synthesis of R-amino acid precursors where it is a standard method with many industrial applications, 4