Selective hydrogenation of α,β-unsaturated oxosteroids with homogeneous rhodium catalysts
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- 作者：Rui M.D. Nunes ; Andreia F. Peixoto ; M. Rosa Axet ; Mariette M. Pereira ; Maria José ; Moreno ; Lá ; szló ; Kollá ; r ; Carmen Claver and Sergio Castilló ; n
- 关键词：Hydrogenation ; Steroid ; Oxosteroid ; Rhodium ; Phosphine ; Phosphite
- 刊名：Journal of Molecular Catalysis A: Chemical
- 出版年：2006
- 出版时间：16 March 2006
- 年：2006
- 卷：247
- 期：1-2
- 页码：275-282
- 全文大小：388 K
文摘
A comparative study of the ligand (5–10) effect on the rhodium catalytic activity and selectivity in the homogeneous hydrogenation of α,β-unsaturated oxosteroids (1–4) is reported. The highest activity for CC reduction was observed with phosphite ligands, being diphosphite 10 the most active. Furthermore, the presence of phosphite 6 significantly enhances the chemo and α-diastereoselectivity for the hydrogenation reaction. The β-methyl groups of the steroidal framework lead to a very high α-diastereoselectivity, even in the absence of phosphorous ligands. Substrate 4 is the paradigm presenting higher than 94 % α-diastereoselectivity for any catalytic system studied.
The catalytic system formed from rhodium and the new diphosphite 10 also revealed a remarkable tendency for the CO reduction and a noteworthy stability.