Citation Analysis Reveals Organic Chemistry's Most Active Research

Following is Science Watch's report, written for the newsletter by John Emsley, who is a science writer in residence at the department of chemistry, Imperial College, London. The article is reprinted here with permission of Science Watch and ISI. Rank 1988 Total Citations 1 E.N. Jacobsen, I. Marko, W.S. Mungall, G. 154 Schroder, K.B. Sharpless, "Asymmetric dihydroxylation via ligand-accelerated catalysis," Journal of the American Chemical Society, 110:1968-70, 1988. 2 Y.-F. Wang, J.J. Lalonde. M. Momongan, D.E. 131 Bergbreiter, C.-H. Wong, "Lipase-catalyzed irreversible transesterifications using enol esters as acylating reagents: Preparative enantio- and regioselective syntheses of alcohols, glycerol derivatives, sugars, and Organometallics," J. Amer. Chem. Soc., 110:7200-5, 1988. 3 D.A. Evans, K.T. Chapman, J. Bisaha, 113 "Asymmetric 113 Diels-Alder cycloaddition reactions with chiral a, b-unsaturated N- acyloxazolidinones," J. Amer. Chem. Soc., 110:1238-56, 1988. 1 E.J. Corey, R. Imwinkelried, S. Pikul, Y.B. 118 Xiang, "Practical 118 enantioselective Diels-Alder and aldol reactions using a new chiral controller system," J. Amer. Chem. Soc. 111:5493-5, 1989. 2 J.S.M. Wai, I. Mark", J.S. Svendsen, M.G. 89 Finn, E.N. Jacobsen, K.B. Sharpless, "A mechanistic insight leads to a greatly improved osmium-catalyzed asymmetric dihydroxylation process," J. Amer. Chem. Soc., 111:1123-5, 1989. 3 D.P. Curran, C.-T. Chang, "Atom transfer 88 cyclization reactions of a-iodo esters, ketones, and malonates: Examples of selective 5-Exo, 6-Endo, 6-Exo, and 7-Endo ring closures," Journal of Organic Chemistry, 54:3140-57, 1989. 1 E. Negishi, S.J. Holmes, J.M. Tour, J.A. Miller, 72 F.E. Cederbaum, D.R. Swanson, T. Takahashi, "Metal-promoted cyclization. 19. Novel bicyclization of enynes and diynes promoted by zirconocene derivatives and conversion of zirconabicycles into bicyclic enones via carbonylation," J. Amer. Chem. Soc., 111:3336-46, 1989.* 2 M. Konishi, H. Ohkuma, T. Tsuno, T. Oki, G.D. 53 VanDuyne, J. Clardy, "Crystal and molecular structure of dynemicin-A: a novel 1,5-Diyn-3- ene antitumor antibiotic," J. Amer. Chem. Soc., 112:3715-6, 1990. 3 D.A. Horne, P.B. Dervan, "Recognition of 53 mixed-sequence duplex DNA by alternate-strand triple-helix formation," J. Amer. Chem. Soc., 112:2435-7, 1990. 1 D.A. Evans, K.A. Woerpel, M.M. Hinman, M.M. 51 Faul, "Bis(oxazolines) as chiral ligands in metal-catalyzed asymmetric reactions: Catalytic, asymmetric cyclopropanation of olefins," J. Amer. Chem. Soc., 113:726-8, 1991. 2 R. Noyori, M. Kitamura, "Enantioselective 50 addition of organometallic reagents to carbonyl compounds: Chirality transfer, multiplication, a and amplification," Angewandte Chemie- International Edition in English, 30:46-9, 1991. 3 H. Fretz, M.W. Albers, A. Galat, R.F. 43 Standaert, W.S. Lane, S.J. Burakoff, B.E. Bierer, S.L. Schreiber, "Rapamycin and FK506 binding proteins (immunophilins)," J. Amer. Chem. Soc., 113:1409-11, 1991. *Article appeared late in 1989 and was not cited until 1990. Source: ISI's Science Indicators Database, 1988-92. In alternating issues, Science Watch reviews the top 10 most-cited papers in chemistry. For more than two years the lists have been dominated by fullerene papers, sometimes exclusively so, with only an occasional paper on organic chemistry making the grade. This is rather odd, because most chemists who are engaged in chemical research are using organic chemistry. Rather than wait for the flood tide of fullerene citations to ebb, Science Watch decided to look beneath the waves and see what pearls of organic chemistry are lying unnoticed. We have combed the ISI lists of highly cited papers for the years 1988 through 1991, specifically seeking those that cover organic topics. The three top-cited papers for each year are listed in the accompanying table. In drawing up the list, I considered only primary research papers and not reviews, which by their very nature collect many citations. Having carried out the citations exercise in organic chemistry, we then needed to check if the topics being cited most really were the hot areas of organic chemistry. I consulted one of Britain's leading organic chemists, Steve Ley of the University of Cambridge, and asked what he regarded as the active areas of organic chemistry at present. His reply was immediate and reassuring: asymmetric synthesis methods, catalytic antibodies, enediynes, taxol, and immunosuppressants, such as rapamycin. The subjects in the table cover three of these current hot topics. The papers featured in the list are from well-known organic chemists: K.B. Sharpless, C.-H. Wong, D.A. Evans, E.J. Corey, D.P. Curran, E. Negishi, P.B. Dervan, R. Noyori, and S.L. Schreiber. Their publications are, for the most part, short communications in the Journal of the American Chemical Society, which attests to the continuing dominance of this primary journal. Asymmetric synthesis accounts for more than half of the subjects in the table, and drug-related research most of the remainder. Two names appear twice: K. Barry Sharpless, formerly of the Massachusetts Institute of Technology and now of the Scripps Research Institute in La Jolla, Calif., and David A. Evans of Harvard University, the former in the top three for 1988 and 1989, the latter in 1988 and 1991. Not all the articles are short communications; witness the 1988 paper on asymmetric synthesis by Evans and colleagues. This runs to 19 pages, of which 10 are devoted to experimental details. His 1991 paper, on the other hand, is less than two pages long. The first of the Evans papers deals with a variant of the Diels-Alder reaction, which was discovered more than 60 years ago as a useful method of synthesis starting with a diene and ending with a cyclic compound. Evans reports that unsaturated N-oxazolidinones make very versatile Diels-Alder reagents. (The oxazolidine ring is five-membered, with a nitrogen and oxygen atom separated by carbon.) These chiral compounds, with various substituents attached to the nitrogen, have several advantages: They are easy to make and are often crystalline; they are highly reactive; and, most important of all, they are diastereoselective, in many cases giving yields of more than 99 percent of the endo isomer. Clearly the significance of Evans's discovery was not lost on others in the field, hence the frequency of citations. His 1991 paper is also devoted to asymmetric synthesis using bis(oxazolines) in which two of these five-membered rings are directly linked, or joined through an intervening carbon. These compounds are used in the form of Cu(I) complexes to catalyze the conversion of styrene to a mixture of cis and trans cyclopropane molecules, again with a marked preference for one of the forms. And what of the future? What topics might we see heading a list of the most-cited papers in organic chemistry in four years' time? For a glimpse into the crystal ball I turned to 41-year-old Tony Barrett, holder of the newly created Glaxo Chair of Chemistry at Imperial College, London. The three topics he thought might be found on such a list were catalytic asymmetric synthesis; non-linear optical materials; and "smart" polymers. Would-be chemistry stars, please note.

Citation Analysis Reveals Organic Chemistry's Most Active Research

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