Asymmetric cyclopropanation catalyzed by fluorous bis(oxazolines)–copper complexes |
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| Affiliation: | 1. Laboratoire de Synthèse Asymétrique, UMR 5181, ESCPE Lyon, Université Claude Bernard Lyon 1, 43, Boulevard du 11 Novembre 1918, 69622 Villeurbanne cédex, France;2. CNR-Istituto di Scienze e Tecnologie Molecolari (ISTM), Via Golgi 19, 201 33 Milano, Italy;1. Menarini Ricerche, Via Tito Speri 10, 00040 Pomezia (Rome), Italy;2. Menarini Ricerche, Via Rismondo12A, 50131 Florence, Italy;3. Dip. di Ingegneria Industriale, Università degli Studi di Firenze, Via Santa Marta 3, 50139 Florence, Italy;1. Department of Chemistry & Pharmaceutical Sciences, Piazzale Europa 1, University of Trieste, 34127 Trieste, Italy;2. Molecular Simulation Engineering (MOSE) Laboratory, DI3, Piazzale Europa 1, University of Trieste, 34127 Trieste, Italy;1. School of Chemical Sciences, Mahatma Gandhi University, Kottayam, 686 560, India;2. Department of Chemistry, St. Berchmans College, Changanacherry, 686 101, India;1. Warsaw University of Technology, Faculty of Chemistry, Noakowskiego 3, 00-664 Warsaw, Poland;2. University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw, Poland |
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| Abstract: | Fluorous bis(oxazoline)–copper(I) complexes generated in situ were tested as catalysts in the metal-catalyzed cyclopropanation of styrene with various α-diazoacetates. Under optimized conditions in CH2Cl2, quite good yields were obtained. Diastereoselectivities were found to be substrate and, to a lesser extent, ligand dependent, with trans/cis ratios ranging from 62/38 (cyclopropanation with α-ethyldiazoacetate 2a using ligand 1a) to 98/2 (cyclopropanation with methyl phenyldiazoacetate 2c using ligand 1b). Enantioselectivities up to 84% ee for the trans-isomer and 81% ee for the cis-isomer were observed using ligand 1b. Fluorous bis(oxazoline)–copper(I) complexes could be very easily separated from the products by simple precipitation using hexane, and recycled without loss of stereo- as well as enantioselectivities. |
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