Scope and Mechanism of the Intermolecular Addition of Aromatic Aldehydes to Olefins Catalyzed by Rh(I) Olefin Complexes
| Autor: | Maurice Brookhart, Amy H. Roy, Christian P. Lenges |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
chemistry.chemical_classification
Aldehydes Olefin fiber Ketone Acylation chemistry.chemical_element Hydroacylation Trimethylsilane General Chemistry Alkenes Ketones Biochemistry Medicinal chemistry Catalysis Reductive elimination Rhodium chemistry.chemical_compound Colloid and Surface Chemistry chemistry Organometallic Compounds Organic chemistry Selectivity |
| Zdroj: | Journal of the American Chemical Society. 129:2082-2093 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja066509x |
| Popis: | Rhodium (I) bis-olefin complexes Cp*Rh(VTMS)(2) and CpRh(VTMS)(2) (Cp* = C(5)Me(5), Cp = C(5)Me(4)CF(3), VTMS = vinyl trimethylsilane) were found to catalyze the addition of aromatic aldehydes to olefins to form ketones. Use of the more electron-deficient catalyst CpRh(VTMS)(2) results in faster reaction rates, better selectivity for linear ketone products from alpha-olefins, and broader reaction scope. NMR studies of the hydroacylation of vinyltrimethylsilane showed that the starting Rh(I) bis-olefin complexes and the corresponding Cp*/Rh(CH(2)CH(2)SiMe(3))(CO)(Ar) complexes were catalyst resting states, with an equilibrium established between them prior to turnover. Mechanistic studies suggested that CpRh(VTMS)(2) displayed a faster turnover frequency (relative to Cp*Rh(VTMS)(2)) because of an increase in the rate of reductive elimination, the turnover-limiting step, from the more electron-deficient metal center of CpRh(VTMS)(2). Reaction of Cp*/Rh(CH(2)CH(2)SiMe(3))(CO)(Ar) with PMe(3) yields acyl complexes Cp*/Rh[C(O)CH(2)CH(2)SiMe(3)](PMe(3))(Ar); measured first-order rates of reductive elimination of ketone from these Rh(III) complexes established that the Cp ligand accelerates this process relative to the Cp* ligand. |
| Databáze: | OpenAIRE |
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