✍ Scribed by Rui M.D. Nunes; Tânia F. Fernandes; Glenda A. Carvalho; Eduardo N. dos Santos; Maria José S.M. Moreno; A.P. Piedade; Mariette M. Pereira
No coin nor oath required. For personal study only.
Macroreticular anion exchange resins, Amberlite IRA-900 and Amberlite IRA-96, were used to bind monosulfonated triphenylphosphine ligand via noncovalent electrostatic interactions. The resin-phosphine system was found to be very efficient at promoting the immobilization of [Rh 2 (-OMe) 2 (cod) 2 ]. The resulting stable Rh/TPPMS immobilized catalyst was tested in the hydrogenation of unsaturated oxosteroids (4-androstene-3,17-dione and 3-acetoxypregna-5,16-dien-20-one). These immobilized catalysts could selectively reduce C C bonds leading to the preferential formation of the ␣-diastereoisomer, as in the homogeneous systems. Furthermore, these new immobilized rhodium catalysts showed good performance, easy separation and recycling without loss of activity after at least three cycles.
When the immobilization of [Rh 2 (-OMe) 2 (cod) 2 ] was carried out in situ using either Amberlyst A27/TPPMS or the polystyrene-block-poly(m-vinyltriphenylphosphine) (PS-b-PPh 3 ), the catalytic activity was lower and a significant decrease was observed on recycling.
📜 SIMILAR VOLUMES
Chiral Ru-BINAP, Rh-DIOP and Rh-BPPM complexes have been physically entrapped in sol-gel matrices. The resulting materials are recyclable leach-proof catalysts for enantioselective hydrogenation of itaconic acid. Chiral methylsuccinic acid of o.p. up to 78% is obtained. The complexes, including the
## Abstract α‐Substituted chiral ketones that have small steric and electronic differences around the reaction sites are difficult substrates to reduce with high diastereoselectivity. Metal hydride reduction of 2‐(4‐benzoylmorpholinyl) phenyl ketone and 3‐(1‐__tert__‐butoxycarbonylpiperidinyl) phen
## Abstract Highly active heterogeneous rhodium hydrogenation catalysts ‐ rhodium on support ‐ have been prepared by pyrolysis of commercially available Rh~4~(CO)~12~, highly dispersed on a suitable support, __e.g.__ SrTiO~3~, TiO~2~‐anatase, TiO~2~‐rutile, BaTiO~3~ or SrZrO~3~. The inactive materi