Rhodium-Catalyzed Hydroformylation of Isoprene: Unusual Accelerating Effects of Phosphorus Ligands and Gas Pressure
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- 作者：Humberto J. V. Barros ; Cristiane C. Guimarã ; es ; Eduardo N. dos Santos ; Elena V. Gusevskaya
- 刊名：Organometallics
- 出版年：2007
- 出版时间：April 23, 2007
- 年：2007
- 卷：26
- 期：9
- 页码：2211 - 2218
- 全文大小：204K
- 年卷期：v.26,no.9(April 23, 2007)
- ISSN：1520-6041
文摘
Rhodium-catalyzed hydroformylation of isoprene has been studied in the presence of various mono-and diphosphines. Using a large excess of the ligand, the reaction can be performed under mild conditions(80-100 
C, 40-80 atm) and results in three unsaturated aldehydes formed in a 95% combined selectivity.The study of the effects of the reaction variables revealed remarkable trends, opposite those usuallyobserved with simple alkenes. The increase in the concentration of the phosphorus ligand and/or ligandbasicity strongly accelerates the reaction. Moreover, the reaction shows unusual kinetics, being first orderin both hydrogen and CO pressure under "common" hydroformylation conditions. The obtained dataconfirm that an 
3-1 rearrangement, which converts an 3-allylrhodium intermediate resistant to COinsertion into the much more reactive 1 complex, is the most critical step of this reaction.
C, 40-80 atm) and results in three unsaturated aldehydes formed in a 95% combined selectivity.The study of the effects of the reaction variables revealed remarkable trends, opposite those usuallyobserved with simple alkenes. The increase in the concentration of the phosphorus ligand and/or ligandbasicity strongly accelerates the reaction. Moreover, the reaction shows unusual kinetics, being first orderin both hydrogen and CO pressure under "common" hydroformylation conditions. The obtained dataconfirm that an 3-1 rearrangement, which converts an 3-allylrhodium intermediate resistant to COinsertion into the much more reactive 1 complex, is the most critical step of this reaction.