trans-[RuCl2(phosphan)2(1,2-diamin)]- und chiraletrans-[RuCl2(diphosphan)(1,2-diamin)]- Komplexe: lagerstabile Katalysatorvorstufen für die schnelle, produktive und stereoselektive Hydrierung von Ketonen

Abstract

Eine Umsatzzahl (TON) von 2 400 000 und einen Umsatz pro Zeit (TOF) von 63 s−1 ermöglicht der chirale RuII‐Komplex 1 (R=p‐H3CC6H4) als Katalysator bei der asymmetrischen Hydrierung von Acetophenon. Mit verwandten RuII‐Katalysatoren werden α,β‐ungesättigte Ketone selektiv an der Carbonylgruppe asymmetrisch hydriert und aus 4‐substituierten Cyclohexanonen die entsprechenden cis‐Alkohole erhalten.

Asymmetric Hydrogenation of Ketones with Polymer-Bound BINAP/Diamine Ruthenium Catalysts

“…[7] At each step, the unreacted materials were removed by washing with DMA. The 31 P NMR analysis [8] of the solid suggested that the resulting diphosphine/diamine mixed-ligand Ru complex (R,RR)-3a was a 7 : 1 mixture of the trans-dichloro complex (singlet at 47.5 ppm) and its cis isomer (broad singlets at 50.0 and 57.5 ppm) contaminated with unreacted (R)-1a (±15.8 ppm) and some unknown compounds. The purity of the diphosphine/diamine Ru complex was ca.…”

“…Both trans-and cis-RuCl 2 [(R)-binap][(R,R)-dpen] are known to be reactive for homogeneous hydrogenation of ketones. [8] As shown in Figure 1, the polymer beads are better swelled in DMF than in 2-propanol, which serves as a standard solvent of hydrogenation. [4] DMA can also be used in place of DMF.…”

“…The ee value was identical to that obtained in the homogeneous system using RuCl 2 [(R)-binap][(R,R)-dpen] in 2-propanol. [8,9] The catalyst was recovered by removing the solution phase by cannula, and reused for hydrogenation. Scheme 2.…”

“…[14] The degree and sense of the enantioselection were comparable with those obtained with RuCl 2 [(R)-binap][(S,S)-dpen]. [8,15] The catalyst was reused seven times without problems, after which the rate was to some extent lowered. The reaction gave a total TON of 27,250, while the product ee was consistently in the range of 93±95% (Table 4).…”

“…[8,21] GC: column temp, 110°C; t R of (R)-7b, 35.4 min (7.8%); t R of (S)-7b, 38.6 min (91.9%); t R of 6b, 21.3 min (0.3%).…”