Asymmetric Hydroformylation of Olefins with Rh Catalysts Modified with Chiral Phosphine-Phosphite Ligands
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- 作者：Miguel Rubio ; André ; s Suá ; rez ; Eleuterio Á ; lvarez ; Claudio Bianchini ; Werner Oberhauser ; Maurizio Peruzzini ; Antonio Pizzano
- 刊名：Organometallics
- 出版年：2007
- 出版时间：December 3, 2007
- 年：2007
- 卷：26
- 期：25
- 页码：6428 - 6436
- 全文大小：249K
- 年卷期：v.26,no.25(December 3, 2007)
- ISSN：1520-6041
文摘
Rhodium complexes stabilized by modularly designed chiral phosphine-phosphite ligands (P-OP)have been tested in the asymmetric hydroformylation of styrene, vinyl naphthalenes, and allyl cyanide.Based on single-crystal X-ray diffraction analysis and NMR studies, restricted aryl rotation has beenfound to characterize ligands 1e and 1f. The outcome of the rhodium-catalyzed hydroformylationreactions is highly dependent on the nature of the two coordinating functions of the phosphine-phosphiteand of the ligand backbone as well. Among the ligands studied, those with an oxyphenylene backboneand PAr2 ends gave the best results, outperforming those with P-stereogenic phosphine groups. The1-naphthyl-substituted catalyst brought about the hydroformylation of styrene with a 71% ee, while thexylyl catalyst afforded the best results in the hydroformylation of allyl cyanide, yielding an iso/n ratioof 13 and 53% ee in the branched isomer. Several hydrido(carbonyl) species of the formulaRhH(CO)2(P-OP) have been generated by reacting Rh(acac)(CO)2/P-OP with syngas. In situ high-pressure NMR experiments showed the phosphine group to occupy an apical position of the trigonalbipyramidal coordination geometry, which allows an aryl-aryl interaction between the phosphinesubstituents and the substrate during the hydroformylation of vinyl arenes. In line with this finding, aremarkable enantioselectivity of 89% ee was obtained with the naphthyl catalyst and 1-vinyl naphthaleneas substrate.