NEWS OF THE WEEK SYNTHESIS
AZIRIDINESVIA ELECTROCHEMISTRY New process offers 'green' route to important synthetic intermediates Yudin
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dines—three-membered rings containing one nitrogen and two carbon atoms—are now accessible through an electrochemical process that requires no metal catalysts or oxidation reagents. Its organic chemist inventors at t h e University of Toronto believe the strategy will be adaptable to a wide range of chemical transformations. Developing synthetic methods that generate minimal amounts of waste has become an important challenge for chemists. So Toronto assistant professor of chemistry Andrei K. Yudin and his graduate student Tung Siu ACS
were hoping to improve a method of preparing aziridines by reducing the amount of lead oxidant it required. "Our initial goal was to learn how to run the reaction with only catalytic amounts of toxic metals such as lead," Yudin tells C&EN. "The thought was that we might find a redox shuttle between lead's oxidation states using electrodes in electron transfer. Fortuitously we discovered that, in the lead-based olefin aziridination, nitrogen transfer can be run using just electricity in the redox Svindow5 where lead(IV) normally operates, with no added lead catalysts or reagents."
NEWS
Society Welcomes Its New Officers
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he American Chemical Society introduced its new officers and board members at a reception on Jan. 22 in Washington, D.C. Guests were greeted by President Eli M. Pearce, President-Elect Elsa Reichmanis, Immediate Past-President Attila E. Pavlath, Executive Director John K Crum, and Board of Directors Chair Nina I. McClelland, as well as ACS Treasurer Brian A. Bernstein and newly elected Secretary Flint H. Lewis. McClelland and Lewis welcomed those in attendance. In a brief address, Pearce highlighted the themes he intends to focus on during his presidency. One of those themes is increasing the number of minority members. Although Pearce pointed out that CHANGING OF THE GUARD the society is "progressing nicely with the way On hand at the ACS new officers women are moving up through its organization and reception were (from left) Crum, the profession," he expressed concern about the Pavlath, ReichmaniSp Pearce, and representation of minorities in chemistry. McClelland. During these times of uncertain job placement and security, Pearce also wants ACS to step up the services it offers its members. He looks to couple an increase in career services with a strong growth in membership, noting that he "wants [the society] to offer so many services that we reach the point where chemists and chemical engineers cannot afford not to be a member of ACS."-SUSAN MORRISSEY
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C & E N / J A N U A R Y 2 8 . 2002
Aziridines are valuable synthetic intermediates because the strained three-membered ring can be opened by a variety of nucleophiles, leading to a pattern of heteroatom substitution that appears regularly in natural products and drugs. Yudin and Siu's approach springs from a common method of making aziridines by metal-mediated transfer of a nitrene to an olefin. The electrochemical strategy which uses two platinum electrodes and a reference silver electrode in a divided cell, employs N-aminophthalimide as the nitrene precursor. It succeeds with a wide range of olefins, both electron-rich and electron-poor [J. Am. Chem. Soc, 124,530(2002)}. Although electrochemical processes are widely used on a massive scale in industry, many organic chemists shy away from them. Yudin thinks that is because electrochemistry tends to be taught in an analytical, rather than organic synthesis, context. He himself learned the subject by reading the book "Synthetic Organic Electrochemistry" by Albert J. Fry, professor of organic chemistry at Wesleyan University Middletown, Conn. Fry comments that the Toronto work is interesting as a new and efficient route to N-phthalimidoaziridines. "But it remains to be seen whether it's a general process for synthesis of aziridines bearing other groups on nitrogen, and in its present form, it does not appear adaptable to synthesis of enantiomerically pure aziridines," he notes. "The need for controlled potential electrolysis and a divided cell will make it difficult to scale up to large quantities in a flow cell." Yudin says his group is already working on enantioselective versions of the reaction and on using other amines and hydrazines as nitrene precursors. T h e researchers are also delving into combinatorial electrosynthesis. [Curr. Opin. Chem. Biol, 5, 2 6 9 (2001)}.-PAMELAZURER HTTP://PUBS.ACS.ORG/CEN
