Mechanistic Dichotomy in the Asymmetric Allylation of Aldehydes with Allyltrichlorosilanes Catalyzed by Chiral Pyridine N‐Oxides |
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| Authors: | Prof?Dr Andrei V Malkov Dr Sigitas Ston?ius Dr Mark Bell Dr Fabiomassimo Castelluzzo Dr Pedro Ramírez‐López Dr Lada Biedermannová Prof?Dr Vratislav Langer Dr Lubomír Rulí?ek Prof?Dr Pavel Ko?ovský |
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| Institution: | 1. Department of Chemistry, WestChem, University of Glasgow, Glasgow G12 8QQ (UK), Fax: (+44)?141‐330‐4888;2. Present address: Department of Chemistry, Loughborough University, Loughborough, Leics LE11 3TU (UK), Fax: (+44)?1509‐22‐3925;3. Present address: Department of Organic Chemistry, Vilnius University, Naugarduko 24, 03225 Vilnius (Lithuania);4. Present address: Drug Discovery Unit, College of Life Sciences, University of Dundee, Dundee, DD1 5EH (UK);5. Present address: ISF, General Medicine Buisness Unit, Bayer S.p.A. Via Orazio Console, n. 103, 000128 Rome (Italy);6. Present address: Department of Organic Chemistry, University of Sevilla, García González 1, 41012 Sevilla (Spain);7. Present address: Institute of Biotechnology, Academy of Sciences of the Czech Republic, Vídeňská 1083, 14220 Prague 4 (Czech Republic);8. Environmental Inorganic Chemistry, Department of Chemical and Biological Engineering, Chalmers University of Technology, 412 96 Gothenburg (Sweden);9. Institute of Organic Chemistry and Biochemistry and Gilead Sciences Research Center, Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 16610 Prague 6 (Czech Republic);10. Sabbatical address: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE 10691 Stockholm (Sweden) |
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| Abstract: | Detailed kinetic and computational investigation of the enantio‐ and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5 , employing the pyridine N‐oxides METHOX ( 9 ) and QUINOX ( 10 ) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate‐ and selectivity‐determining step, which is supported by both experimental and computational data. |
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| Keywords: | allylation allylsilanes calculations organocatalysis pyridine N‐oxides |
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