Arene–ruthenium complexes with salicyloxazolines: diastereoselective synthesis, configurational stability and applications as asymmetric catalysts for Diels–Alder reactions
| Autor: | Adam J. Davenport, David L. Davies, David R. Russell, John Fawcett |
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| Rok vydání: | 2004 |
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| Zdroj: | Dalton Trans.. :1481-1492 |
| ISSN: | 1477-9234 1477-9226 |
| Popis: | Reaction of the dimers [RuCl2(η6-arene)]2 (arene = benzene, p-cymene, mesitylene) with salicyloxazolines in the presence of NaOMe gives complexes [RuCl(R-saloxaz)(arene)] (1–5) which have been fully characterised. Complexes [RuL(iPr-saloxaz)(mes)]Y (L = py, 2-Mepy, 4-Mepy; PPh3; Y− = SbF6 or BPh4) 6–9 were prepared by treating the chloride 2a with ligand L and NaY (Y− = SbF6 or BPh4) in methanol at reflux. Halide complexes [RuX(iPr-saloxaz)(mes)] (X = Br, 10; X = I, 11) were synthesised by treating 2a with AgSbF6 then with 1.2 equivalents of KBr or NaI, the methyl complex [RuMe(iPr-saloxaz)(mes)] 12 was synthesised from 2a by reaction with MeLi. Five complexes, [RuCl(iPr-saloxaz)(mes)] 2a, [RuCl(tBu-saloxaz)(p-cymene)] 3b, [RuCl(Ph-saloxaz)(mes)] 5a, [Ru(4-Mepy)(iPr-saloxaz)(mes)][SbF6] 7, and [Ru(PPh3)(iPr-saloxaz)(mes)][SbF6] 9, have been characterised by X-ray crystallography. Treatment of complexes 1–5 with AgSbF6 gives cationic species which are enantioselective catalysts for the Diels–Alder reaction of acroleins with cyclopentadiene, the effect of substituents on enantioselectivity has been examined. |
| Databáze: | OpenAIRE |
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