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December 10, 2001
Volume 79, Number 50
CENEAR 79 50 pp. 45-55
ISSN 0009-2347
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[Previous Story] [Next Story]CHEMISTRY HIGHLIGHTS 2001

CATALYSIS. The development of new catalysts and catalyst technologies continues to be a strong focus of chemical research. Important developments in 2001 included microarray-based enantioselectivity measurements, a soluble catalyst that oxidizes organic compounds in air, "green" catalysts that generate benign water as a by-product--and the Nobel Prize in Chemistry.

High-throughput screening of compound libraries to discover new enantioselective catalysts has been impeded by the lack of rapid and convenient techniques for determining a prospective catalyst's enantioselectivity--the extent to which it favors one enantiomeric product over another. But graduate students Gregory A. Korbel and Gojko Lalic and assistant professor Matthew D. Shair of the department of chemistry and chemical biology and the Center for Genomics Research at Harvard University devised a microarray method for measuring such enantioselectivities rapidly [J. Am. Chem. Soc., 123, 361 (2001); C&EN, Jan. 15, page 9]. In the technique, enantiomeric products are covalently attached to chiral groups spotted on a glass slide. Fluorescent chiral probe reagents that react with the enantiomers are added, the resulting fluorescence is monitored, and the absolute configuration and enantiomeric excesses of the products from each spot are determined.

Emory University chemistry professor Craig L. Hill and coworkers Eric Boring and Yurii V. Geletii discovered a soluble catalyst that uses oxygen in air to catalyze the selective oxidation of thioethers to sulfoxides under ambient conditions [J. Am. Chem. Soc., 123, 1625 (2001); C&EN, March 5, page 11]. Potential applications include cosmetics, coatings, and fabrics that catalytically destroy contaminants in air. The new catalyst works orders of magnitude faster than the best previously known soluble O2-based oxidation catalysts, which are active only at elevated temperatures.

Chemist Ira A. Weinstock at USDA's Forest Products Laboratory, Hill at Emory, and coworkers also reported an environmentally benign and stable polyoxometalate catalyst system that selectively oxidizes organic substrates with O2 (or air) in aqueous media [Nature, 414, 191 (2001); C&EN, Nov. 12, page 5]. The researchers used the system to develop the first process for delignification of wood (conversion of wood to paper) that is liquid waste free.

Two other research groups independently made progress this year toward the development of environmentally friendly catalysts for oxidizing organic compounds (C&EN, July 23, page 9). Chemistry professor Eric N. Jacobsen of Harvard University and coworkers developed a new catalyst for the high-yield conversion of olefins to racemic epoxides [J. Am. Chem. Soc., 123, 7194 (2001)]. And the group of chemistry professor Lawrence Que Jr. at the University of Minnesota, Minneapolis, devised a catalyst for the enantioselective dihydroxylation of olefins [J. Am. Chem. Soc., 123, 6722 (2001)]. Both groups' catalysts are ethylenediamine-based ligands bound to iron. The ligands are inexpensive and simple to make, and the new reactions use hydrogen peroxide as an oxidizing agent and thus produce environmentally benign water as a by-product.

In Spain, Polytechnic University of Valencia chemistry professor Avelino Corma and colleagues developed another environmentally friendly catalyst--one that accelerates the Baeyer-Villiger reaction, which is widely used industrially to oxidize ketones to lactones or esters. The conventional form of the reaction often produces considerable acid waste, but the zeolite-tin catalyst devised by Corma and coworkers uses hydrogen peroxide as an oxidizer and thus (as in the two epoxidation reactions described above) yields harmless water as a by-product [Nature, 412, 423 (2001); C&EN, July 30, page 14].

This was also the year in which chiral catalysis was honored by a Nobel Prize in Chemistry (C&EN, Oct. 15, page 5). The prize was shared by Monsanto retiree William S. Knowles and chemistry professor Ryoji Noyori of Nagoya University, Japan, for their work on catalytic asymmetric hydrogenations, and chemistry professor K. Barry Sharpless of Scripps Research Institute for his studies on catalytic asymmetric oxidations. All three discovered chiral catalysts for the production of single-enantiomer compounds. According to the Royal Swedish Academy of Sciences, Stockholm, the discoveries "have had a very great impact on academic research and the development of new drugs and materials and are used in many industrial syntheses of drugs and other biologically active compounds."


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