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Aldrichimica Acta, Please Contact Us By: Phone: 800-325-3010 (USA) Synthesis and Applications of Diorganozinc Reagents: Beyond Diethylzinc

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Aldrichimica Acta, Please Contact Us By: Phone: 800-325-3010 (USA) Synthesis and Applications of Diorganozinc Reagents: Beyond Diethylzinc OPENING NEW FRONTIERS IN SYNTHESIS AND CATALYSIS VOL. 42, NO. 3 • 2009 Discovering New Reactions with N-Heterocyclic Carbene Catalysis Synthesis and Applications of Diorganozinc Reagents: Beyond Diethylzinc New Products from Aldrich R&D Aldrich Is Pleased to Offer Cutting-Edge Tools for Organic Synthesis Phosphine for the Conversion of Azides into Diazo Compounds More NEW Solutions of Common Reagents Due to difficulties with their preparation, especially when sensitive functional Every researcher has experienced the frustration of using on a regular basis some groups are present, diazo compounds are often overlooked in synthesis despite lab reagent that is annoying to handle: It might be difficult to weigh out, extremely their synthetic versatility. Myers and Raines have developed a mild method to volatile, prone to static, or noxious. Sigma-Aldrich has designed a series of solutions convert an azido group with delicate functional groups into a diazo compound intended to make many of these common reagents easier to measure, handle, by using the phosphine reagent shown below. Formally, this reaction is a and dispense. reductive fragmentation of the azide, like the venerable Staudinger reaction, and is highly selective in most chemical environments. 2,2′-Azobis(2-methylpropionitrile) solution, 0.2 M in toluene 714887 100 mL H3C CH3 [78-67-1] N C N O N C N C8H12N4 O H3C CH3 N FW: 164.21 P O O Iodine monochloride, 1 M in acetic acid 714836 100 mL 1.05 equiv [7790-99-0] ICl 715069 ICl N N 3 1) THF/H2O (20:3), 3-12 h 2 FW: 162.36 1 2 1 2 R R 2) Sat. aq. NaHCO3, 15 min - 12 h R R 49 - 97% 4-(Dimethylamino)pyridine solution, 0.5 M in ethyl acetate 714720 H C CH 100 mL 3 N 3 [1122-58-3] C H N Myers, E. L; Raines, R. T. Angew. Chem., Int. Ed. 2009, 48, 2359. 7 10 2 FW: 122.17 N N-Succinimidyl 3-(diphenylphosphino)propionate, 95% 4-(Dimethylamino)pyridine solution, 0.5 M in THF 715069 O 1 g O 714844 H3C CH3 100 mL [170278-50-9] N 5 g N C H NO P P O [1122-58-3] 19 18 4 O C H N FW: 355.32 7 10 2 FW: 122.17 N 1,8-Diazabicyclo[5.4.0]undec-7-ene solution, 1 M in ethyl acetate 714860 100 mL Stable Precursor for Nazarov’s Reagent [6674-22-2] N Nazarov’s reagent is a commonly used annulating agent, but its synthesis is often C9H16N2 N fraught with poor yields or difficulties isolating the material. De Risi and coworkers FW: 152.24 recently reported a bench-stable powder that can be demasked under various conditions to generate Nazarov’s reagent in situ. 1,8-Diazabicyclo[5.4.0]undec-7-ene solution, 1 M in THF 714852 100 mL O [6674-22-2] N C H N O O O 9 16 2 N O H3C O FW: 152.24 H3C S OEt O KF, MeOH, rt, 24 h O Acetaldehyde solution, 5 M in THF 718327 CO2Et 719099 50 mL 50% [75-07-0] O C2H4O H3C H Benetti, S. et al. Synlett 2008, 2609. FW: 44.05 Ethyl 5-[(4-methylphenyl)sulfonyl]-3-oxopentanoate, 95% Carbon disulfide, 5 M in THF 718327 O O 1 g 721476 50 mL O C H O S [75-15-0] 14 18 5 H3C S OEt CS2 FW: 298.35 O CS2 FW: 76.14 sigma-aldrich.com 53 “PLEASE BOTHER US.” VOL. 42, NO. 3 • 2009 Joe Porwoll, President Aldrich Chemical Co., Inc. Aldrich Chemical Co., Inc. Sigma-Aldrich Corporation 6000 N. Teutonia Ave. Milwaukee, WI 53209, USA Dr. Biagetti Matteo from GlaxoSmithKline kindly suggested that we make lithium diisobutyl- t-butoxyaluminum hydride (LDBBA). LDBBA is an effective reducing agent for the conversion of esters into aldehydes without the problematic over-reduction or the inconvenience of To Place Orders requiring lower temperatures. Telephone 800-325-3010 (USA) Kim, M. S.; Choi, Y. M.; An, D. K. Tetrahedron Lett. 2007, 48, 5061. FAX 800-325-5052 (USA) or 414-438-2199 Mail P.O. Box 2060 Al Milwaukee, WI 53201, USA O H Li Customer & Technical Services Customer Inquiries 800-325-3010 718386 Technical Service 800-231-8327 718386 Lithium diisobutyl-t-butoxyaluminum hydride (LDBBA), SAFC® 800-244-1173 0.5 M in THF-hexanes 25 mL Custom Synthesis 800-244-1173 100 mL Flavors & Fragrances 800-227-4563 International 414-438-3850 Naturally, we made this useful reducing agent. It was no bother at all, just a 24-Hour Emergency 414-438-3850 pleasure to be able to help. Website sigma-aldrich.com Email [email protected] Do you have a compound that you wish Aldrich could list, and that would help you in your research by saving you time and money? If so, please send us your suggestion; we will be delighted General Correspondence to give it careful consideration. You can contact us in any one of the ways shown on this page and Editor: Sharbil J. Firsan, Ph.D. on the back cover. P.O. Box 2988, Milwaukee, WI 53201, USA TABLE OF CONTENTS Subscriptions Discovering New Reactions with N-Heterocyclic Carbene Catalysis............................. 55 To request your FREE subscription to the Eric M. Phillips, Audrey Chan, and Karl A. Scheidt,* Northwestern University Aldrichimica Acta, please contact us by: Phone: 800-325-3010 (USA) Synthesis and Applications of Diorganozinc Reagents: Beyond Diethylzinc .............. 71 Alexandre Lemire, Alexandre Côté, Marc K. Janes, and André B. Charette,* University of Montreal Mail: Attn: Mailroom Aldrich Chemical Co., Inc. Sigma-Aldrich Corporation ABOUT OUR COVER P.O. Box 2988 Paul Cézanne (1839–1906), who painted Milwaukee, WI 53201-2988 Landscape near Paris (oil on canvas, Email: [email protected] 50.2 × 60 cm) around 1876, was born in Aix-en-Provence in 1839. His father, a International customers, please contact your local Sigma- prosperous businessman, decided that Aldrich office. For worldwide contact infor mation, please see his only son should become a lawyer. the back cover. Cézanne attended the Aix law school, but preferred classes at the Musée d’Aix (now The Aldrichimica Acta is also available on the Internet at the Musée Granet) and decided on a life as sigma-aldrich.com/acta. an artist instead. In 1861, Cézanne, encouraged by his Aldrich brand products are sold through Sigma-Aldrich, Inc. boyhood friend, the novelist Émile Zola, Sigma-Aldrich, Inc., warrants that its products conform to traveled to Paris. There, he frequented the Salon, studied the old masters, and copied Photograph © Board of Trustees, National Gallery of Art, Washington. the information contained in this and other Sigma-Aldrich Delacroix at the Louvre. He also forged publications. Purchaser must determine the suitability of the friendships with many important artists, one of whom, Camille Pissarro, became a pivotal, product for its particular use. See reverse side of invoice or lifelong influence on Cézanne. packing slip for additional terms and conditions of sale. Cézanne exhibited with the impressionists in 1874 and 1877. Our cover possibly painted in the company of Pissarro in Auvers-sur-Oise, a northwestern suburb of Paris, was completed All prices listed in this publication are subject to change sometime between the two exhibitions. The work clearly denotes Cézanne’s departure from without notice. his early romantic and realist influences, and displays his enduring interest in plein-air painting. Aldrichimica Acta (ISSN 0002-5100) is a publication of In this work, Cézanne placed an emphasis on the observation of nature and the rendering of Aldrich. Aldrich is a member of the Sigma-Aldrich Group. light and atmospheric effects. He achieved structure by applying paint directly to the canvas, © 2009 Sigma-Aldrich Co. recording his response to the sensation of color. This painting is part of the Chester Dale Collection at the National Gallery of Art, Washington, DC. VOL. 42, NO. 3 • 2009 N-Heterocyclic Carbene Organocatalysts Organocatalysis has been an active field of research with Recently, Phillips et al. reported the utilization of a chiral over 2,000 publications in the past 10 years. Interest in this triazole for the enantioselective addition of homoenolates relatively new field derives from the many advantages of to nitrones affording γ-amino esters. This reaction is very organocatalysis such as easy experimental procedures, versatile and tolerates electron-rich and electron-poor reduction of chemical waste, avoidance of metal groups on the aldehyde. Using 20 mol % of the chiral contamination in the product, and cost saving from not triazole at –25 °C affords the desired products in good yields using expensive metals for the catalysis. and selectivities. Scheidt and coworkers have developed a series of N-heterocyclic carbene organocatalysts for various BF4 reactions. These catalysts are efficient, and the chiral ones N N have given rise to good enantioselectivities. N O In 2005, Audrey Chan and Karl A. Scheidt reported the 708542 O transformation of unsaturated aldehydes into saturated O O Ph (20 mol %) H3CO OH H N esters in good yields by using as low as 5 mol % of an + N CH Cl , Et N, 25 °C Ph Ph Ph R H 2 2 3 − N-heterocyclic carbene catalyst. then NaOMe/MeOH R R = aryl, Cy 62–80% 81–93% ee I O N N Reference: O O Phillips, E. HM.3 COet al. J. Am. Chem.OH Soc. 2008H,3 130CO, 2416. OH H3CO OH N N N Ph Ph Ph Ph 708593 Ph Ph H CO Ph (5 mol %) 3 O O PhOH (2 eq.) 70%, 93% ee 70%, 93% ee 62%, 90% ee + ROH Ph H Ph OR DBU, toluene BF4 BF4 O O O O Ph N N N N Ph OEt Ph OPh Ph O Ph O N N O O 72% 56% 57% 77% 708542 708569 Reference: Chan, A.; Scheidt, K.
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