Cuervo Darío, Gamasa M Pilar, Gimeno José
Departamento de Química Orgánica e Inorgánica, Instituto de Química Organometálica "Enrique Moles", (Unidad Asociada al C.S.I.C.), Facultad de Química, Universidad de Oviedo, c/Julián Clavería s/n, 33071 Oviedo, Spain.
Chemistry. 2004 Jan 23;10(2):425-32. doi: 10.1002/chem.200305170.
Treatment of complex trans-[RuCl(2)(eta(2)-C(2)H(4))[kappa(3)-N,N,N-(R,R)-Ph-pybox]] [(R,R)-Ph-pybox = 2,6-bis[4'-(R)-phenyloxazolin-2'-yl]pyridine] with phosphines or phosphites in dichloromethane at 50 degrees C leads to the formation of novel ruthenium(II)-pybox complexes trans-[RuCl(2)(L)[kappa(3)-N,N,N-(R,R)-Ph-pybox]] [L = PPh(3) (1 a), PPh(2)Me (2 a), PPh(2)(C(3)H(5)) (3 a), PPh(2)(C(4)H(7)) (4 a), PMe(3) (5 a), PiPr(3) (6 a), P(OMe)(3) (7 a) and P(OPh)(3) (8 a)]. Likewise, reaction of trans-[RuCl(2)(eta(2)-C(2)H(4))[kappa(3)-N,N,N-(R,R)-Ph-pybox]] with PPh(3) or PiPr(3) in refluxing methanol leads to the complexes cis-[RuCl(2)(L)(kappa(3)-N,N,N-(R,R)-Ph-pybox] [L = PPh(3) (1 b), PiPr(3) (6 b)]. No trans-cis isomerisation of complexes 1 a-8 a has been observed. Complexes 1 a-8 a, 1 b, 6 b together with the analogous trans-[RuCl(2)[P(OMe)(3)][kappa(3)-N,N,N-(S,S)-iPr-pybox]] (10 a) and the previously reported trans- and cis-[RuCl(2)(PPh(3))[kappa(3)-N,N,N-(S,S)-iPr-pybox]] (9 a and 9 b, respectively) are active catalysts for the transfer hydrogenation of acetophenone in 2-propanol in the presence of NaOH (ketone/cat/NaOH 500:1:6). cis-Ph-pybox derivatives are the most active catalysts. In particular, cis complexes 1 b and 6 b led to almost quantitative conversions in less than 5 min with a high enantioselectivity (up to 95 %). A variety of aromatic ketones have also been reduced to the corresponding secondary alcohols with very high TOF and ee up to 94 %. The overall catalytic performance seems to be a subtle combination of the steric and/or electronic properties both the phosphines and the ketones. A high TOF (27 300 h(-1)) and excellent ee (94 %) have been found for the reduction of 3-bromoacetophenone with catalyst 6 b. Reductions of alkyl ketones also proceed with high and rapid conversions but low enantioselectivities are achieved.
在50℃下，将配合物反式-[RuCl₂(η²-C₂H₄)[κ³-N,N,N-(R,R)-Ph-pybox]] [[(R,R)-Ph-pybox = 2,6-双[4'-(R)-苯基恶唑啉-2'-基]吡啶]与膦或亚磷酸酯在二氯甲烷中反应，生成新型钌(II)-pybox配合物反式-[RuCl₂(L)[κ³-N,N,N-(R,R)-Ph-pybox]] [L = PPh₃ (1 a), PPh₂Me (2 a), PPh₂(C₃H₅) (3 a), PPh₂(C₄H₇) (4 a), PMe₃ (5 a), PiPr₃ (6 a), P(OMe)₃ (7 a) 和P(OPh)₃ (8 a)]。同样，反式-[RuCl₂(η²-C₂H₄)[κ³-N,N,N-(R,R)-Ph-pybox]]与PPh₃或PiPr₃在回流甲醇中反应，生成配合物顺式-[RuCl₂(L)(κ³-N,N,N-(R,R)-Ph-pybox] [L = PPh₃ (1 b), PiPr₃ (6 b)]。未观察到配合物1 a - 8 a的反-顺异构化。配合物1 a - 8 a、1 b、6 b以及类似的反式-[RuCl₂[P(OMe)₃][κ³-N,N,N-(S,S)-iPr-pybox]] (10 a)和先前报道的反式和顺式-[RuCl₂(PPh₃)[κ³-N,N,N-(S,S)-iPr-pybox]] (分别为9 a和9 b)是在NaOH存在下于2-丙醇中对苯乙酮进行转移氢化反应的活性催化剂(酮/催化剂/NaOH为500:1:6)。顺式-Ph-pybox衍生物是最具活性的催化剂。特别是，顺式配合物1 b和6 b在不到5分钟内导致几乎定量的转化，具有高对映选择性(高达95%)。多种芳香酮也已被还原为相应的仲醇，具有非常高的TOF和高达94%的ee值。整体催化性能似乎是膦和酮的空间和/或电子性质的微妙组合。用催化剂6 b还原3-溴苯乙酮时发现具有高TOF(27300 h⁻¹)和优异的ee(94%)。烷基酮的还原反应也以高且快速的转化率进行，但对映选择性较低。
