Rainer Stürmer

Take the Right Catalyst: Palladium-Catalyzed C−C, C−N, and C−O Bond Formation on Chloroarenes

Unreactive chloroarenes have been outwitted: The key to successful C-C, C-N, and C-O bond formation on chloroarenes is the development and optimization of suitable catalysts. Electron-rich alkylphosphanes are mandatory as ligands in these palladium-catalyzed reactions.

Synthesis of the first water-soluble chiral tetrahydroxy diphosphine Rh(I) catalyst for enantioselective hydrogenation

The synthesis of the first chiral polyhydroxy diphosphine-Rh(I) catalyst for asymmetric hydrogenation is described. Based on a simple synthetic pathway starting from d-mannitol the new metal complex is constructed. A special feature of the approach is the protection of the air-sensitive phosphine groups by the catalytically active metal in the final synthetic steps. Therefore, tedious P-protection-deprotection procedures could be advantageously avoided. The new water-soluble catalyst hydrogenates functionalized olefins by up to 99.6% ee in water as solvent.

Der richtige Katalysator macht's: palladiumkatalysierte Cl‐Substitution an Chlorarenen unter Bildung von C‐C‐, C‐N‐ und C‐O‐Bindungen

Die bei katalytischen Umsetzungen reaktionstragen Chlorarene wurden „uberlistet”. Schlussel zum Erfolg bei den schematisch gezeigten C-C-, C-N- und C-O-Bindungsknupfungen ist der Einsatz von elektronenreichen Alkylphosphanen als Liganden fur das katalytisch aktive Palladium.

Synthesis of Chiral 2,5-Bis(oxymethyl)-Functionalized Bis(phospholanes) and Their Application in Rh- and Ru-Catalyzed Enantioselective Hydrogenations

The synthesis of a series of chiral 2,5-bis(oxymethyl)-substituted bis(phospholanes) 13a−c and 15a,b (BASPHOS) is described, representing functionalized derivatives of the prominent DuPHOS or BPE ligands. D-Mannitol was used as the starting material for these ligands. New bisphospholanes were used as ligands in the enantioselective rhodium(I)-catalyzed hydrogenation of functionalized olefins like unsaturated α- and β-amino acid derivatives, itaconates, and an unsaturated phosphonate. A relevant ruthenium(II) catalyst was used for the reduction of prochiral β-oxo esters. The enantioselectivities, ranging from 8−99% ee, were strongly dependent on the type of the substituent on the oxymethyl group as well on the bridge connecting the phospholane units.

Optically active titanium complexes containing a tridentate linked amido-cyclopentadienyl ligand.

Optically active titanium complexes Tieta5:eta1-C5R4SiMe2NC6H10 (OCH2Ph)-2Cl2 (R = H, Me), containing a cyclopentadienyl ligand linked to the chiral trans-2-benzyloxycyclohexylamido group, were synthesized and characterized in both enantiomerically pure forms. A single crystal X-ray structure analysis of (-)-(R, R)-Tieta5:eta1-C5H4SiMe2NC6H10(OCH2Ph)-2Cl2 shows a structure in which the benzyloxy group in the amido sidechain is not interacting with the titanium center. Upon activation with n-butyllithium, these complexes hydrogenate acetophenone N-benzylimine with low enantioselectivity.

A phenyl-assisted asymmetric iodolactonisation reaction

Iodo-lactonisation of the allylic carbonate 2 proceeded with high diastereoselectivity to give the iodocarbonate 3. Iodine attacked the double bond in 2 from the face, which is flanked by the phenyl group. This suggests an activating effect of the phenyl group in this reaction.