Title: A Catalytic, Me<sub>2</sub>Zn‐Mediated, Enantioselective Reformatsky Reaction With Ketones
Abstract: Angewandte Chemie International EditionVolume 45, Issue 18 p. 2951-2954 Communication A Catalytic, Me2Zn-Mediated, Enantioselective Reformatsky Reaction With Ketones† Pier Giorgio Cozzi Prof. Dr., Pier Giorgio Cozzi Prof. Dr. [email protected] Dipartimento di Chimica "G. Ciamician", Università di Bologna, Via Selmi, 2, 40126 Bologna, Italy, Fax: (+39) 051-209-9456Search for more papers by this author Pier Giorgio Cozzi Prof. Dr., Pier Giorgio Cozzi Prof. Dr. [email protected] Dipartimento di Chimica "G. Ciamician", Università di Bologna, Via Selmi, 2, 40126 Bologna, Italy, Fax: (+39) 051-209-9456Search for more papers by this author First published: 21 April 2006 https://doi.org/10.1002/anie.200504239Citations: 69 † Dr. Eleonora Rivalta is acknowledged for her experimental help. Professor Giuseppe Bartoli and Dr. Paolo Melchiorre are acknowledged for allowing use of their chiral GC instruments. The European Commission (project FP6-505267-1(LIGBANK)), MIUR (Progetto Nazionale Stereoselezioni in Chimica Organica: Metodologie ed Applicazioni), and FIRB (Progettazione, preparazione e valutazione biologica e farmacologica di nuove molecole organiche quali potenziali farmaci innovativi) are acknowledged for their financial support of this research. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract Kill two birds with one …︁ Salen! A catalytic and practical Me2Zn-mediated enantioselective Reformatsky reaction promoted by [ClMn(salen)] with a ketone as the electrophile is presented (see scheme). The broad scope and simple nature of this procedure, which allows the use of commercially available starting materials and leads to useful building blocks containing quaternary stereocenters, make it extremely attractive. (salen=N,N′-ethylenebis(salicylideneamine).) Supporting Information Supporting Information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z504239_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. References 1S. Reformatsky, Ber. Dtsch. Chem. Ges. 1887, 20, 1210–1211; for a review, see: R. Ocampo, W. R. 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Lett. 2001, 254–255. 14Binol, N-methylephedrine, pybox, sparteine, bis-sulfonamides, bis-imines, taddol, box, binap, and hydroxyphenyloxazoline employed in a model reaction in Et2O as the reaction solvent with PhCOMe, iodoacetate, and Me2Zn gave no conversion after 24 h. 15Different chiral or achiral salen-type ligands (0.1 equiv) were tested in the presence of PhCOMe (1 equiv) and Me2Zn (2 equiv) in Et2O as the solvent. 16The absolute configuration of the product was established by comparing the optical rotation with that of a known product, see: M. Guetté, J. Capillon, J.-P. Guettè, Tetrahedron 1973, 29, 3659–3667. 17[ClMn(salen)] was prepared according to: M. Palucki, N. S. Finney, P. J. Pospisil, M. L. Guler, T. Ishida, E. N. Jacobsen, J. Am. Chem. Soc. 1998, 120, 948–954, and references therein. Commercially available [ClMn(salen)] shows higher reactivity but slightly lower enantioselectivity (see Supporting Information (Table 3, entry 5)). Differences in performance for catalytic epoxidation with commercially available [ClMn(salen)] have also been observed and are probably due to the presence of oxo compounds, see: J. R. Chipperfield, J. Clayton, K. A. Siraj, S. Woodward, J. Chem. Soc. Dalton Trans. 2000, 1087–1094, and references therein. 18E. McGarrigle, D. G. Gilheany, Chem. Rev. 2005, 105, 1563–1602. 19Schiff bases with hindered groups in positions 2 and 2′ give better results. This could be related to the stability of Mn(salen) in the presence of an excess of Me2Zn. For the relative stability of metal–Schiff base complexes in the presence of other metal complexes, see: E. Solari, F. Corazza, C. Floriani, A. Chiesi-Villa, C. Guastini, J. Chem. Soc. Dalton Trans. 1990, 1345–1355. 20Increasing the reaction time at reflux gave a lower yield and complete conversion of the ketone. 21For radical reactions mediated by MnIII, see: 21aT. Linker, J. Organomet. Chem. 2002, 661, 159–167; 21bK. Narasaka, Pure Appl. Chem. 1997, 69, 601–604; 21cD. Yang, X.-Y. Ye, S. Gu, M. Xu, J. Am. Chem. Soc. 1999, 121, 5579–5580. 22For the use of [ClMn(salen)] as a Lewis acid, see: 22aS. S. Kim, S. H. Lee, Synth. Commun. 2005, 35, 751–759. 23The reaction with benzaldehyde following the optimized protocol afforded the desired product with 40 % ee. We are now studying different salen ligands in order to improve the enantiomeric excess with aldehydes. 24S. Mitsui, Y. Kudo, Tetrahedron 1967, 23, 4271–4277. 25I. Dyong, D. Glittemberg, Chem. Ber. 1977, 110, 2721–2728. 26K. Y.-K. Chow, J. Bode, J. Am. Chem. Soc. 2004, 126, 8126–8127. Citing Literature Volume45, Issue18April 28, 2006Pages 2951-2954 ReferencesRelatedInformation