MEETING BRIEFS FROM DALLAS
3
H 3 -Methyl iodide synthesis improved An efficient preparation of tritritiomethyl iodide for isotopic labeling has been devised by organic chemist Manouchehr Saljoughian of the National Tritium Labeling Facility at Lawrence Berkeley Laboratory, in California. Working with chemists Hiromi Morimoto, Philip G. Williams, and Henry Rapoport, he chlorinated 4-biphenylyl chlorothiocarbonate to get 4-trichloromethoxybiphenyl. This solid ether is stable, and its use minimizes the number of radioactive intermediates. Reaction of the ether with tritium using palladium-charcoal catalyst and 1,8-bis(dimethylamino)naphthalene produced 4-3H3-methoxybiphenyl. Cleavage of this compound with hydrogen iodide yielded 3H3-methyl iodide of very high specific activity. The National Institutes of Health supported the work. Ammonium formate gives fast reductions Catalytic transfer hydrogenolysis with ammonium formate is sufficiently fast and selective to make compounds labeled with short-lived isotopes, according to organic chemist Siya Ram of Duke University Medical Center, Durham, N.C. Chemists try to complete syntheses of radiochemicals within three half-lives of the isotope. Ram made α-amino acids for positron emission tomography by reaction of nitroalkanes with carbon-11 dioxide (half-life 20.5 minutes), followed by reduction with ammonium formate and palladium-charcoal catalyst. Reduction time was 10 minutes. Cyano, keto, ester, and amide groups are unaffected. α,/3-Unsaturated carbonyl compounds yield saturated derivatives. On heating at low pH, ketones are reduced to hydrocarbons. Borane reactions finished with perborate Sodium perborate is gentler than the usual 3 0 % hydrogen peroxide and 3Λ/ sodium hydroxide in workups of such borane reactions as hydroborations and reductions, according to organic chemistry professor George W. Kabalka of the University of Tennessee, Knoxville. Working with postdoctoral fellows Timothy M. Shoup and Naganna M. Goudgaon, he made fatty acid and steroid derivatives with ester, nitrile, sulfoxide, and thiol ether groups in as high or higher yield than the usual approach. For example, hydroboration of methallyl chloride gave 80 to 9 0 % of 3-chloro-2-methylpropanol, compared with 3 5 % with hydrogen peroxidesodium hydroxide. The Department of Energy supported the work. Heterocyclic rings closed electrochemically A synthesis of heterocyclic compounds based on cyclization of electrochemically generated nitrogen radicals has been developed by organic chemists at Merck & Co., Rahway, N.J. Though explored to date for only one ring system, the method may be widely applicable. Sandor Karady said that he, Edward G. Corley, Newton L. Abramson, and Leonard M. Weinstock electrolyzed a solution of, for example, 75 g of 5-a(^oxylaminch5-methyl-5AWibenzo[a^ycloheptene at 1.2 volts and 50 to 80 milliamp per sq cm to get a 7 0 % yield of 42
April 24, 1989 C&EN
8-acetoxy-1-methyl-2,3,6,7-dibenzo-8-azabicyclo[3.2.1] octan4-ol. Karady proposed a one-electron oxidation to an acetoxylaminium radical cation, which adds to the olefinic bond with loss of a proton, yielding an alky I radical at the other carbon. A one-electron oxidation of the radical forms a carbonium ion, which reacts with water to give the alcohol. Method functionalizes aromatic side chains A possibly commercial method to produce benzylic alcohols, aldehydes, or acylophenones from alkylated aromatics comes from Interox America, Deer Park, Tex. According to Interox America marketing specialist Martin Jeff, the process goes equally well with electron-donating or electron-withdrawing substituents. Working with organic chemists Kevan Reeve and William Sanderson at Interox U.K., Widnes, Cheshire, Jeff reacted toluenes with 35 to 7 0 % hydrogen peroxide and 48 % hydrobromic acid in refluxing chlorinated solvents to get α-bromo or α,α-dibromo derivatives. Hydrolysis yielded the oxygenated products. Continuous reoxidation of hydrogen bromide to bromine by hydrogen peroxide allowed use of all the bromine. The researchers initiated reactions by photolysis or with such compounds as benzoyl peroxide or bis(4-fertbutylcyclohexyl) peroxydicarbonate. The firm will both license the technology to others and perform custom syntheses. Organophosphazine trimer gives high polymer Inorganic chemist Harry R. Allcock and coworkers at Pennsylvania State University have found a way to make high polymers from cyclic organophosphazine trimers of the type (NPR2)3, where R is an alky I group. Previous attempts to convert such trimers into high-molecular-weight polymers had failed, and it was assumed that halogen atoms on the phosphorus were necessary for the ring-opening polymeri zation. The key to Allcock's latest success involves ring strain and catalysis. A ring-spanning ferrocenyl unit was used to induce strain in a phosphazine trimer bearing trifluoroethoxy groups. When this compound was heated at 250 °C in the presence of a catalytic amount of the cyclic trimer (NPCI2)3, the poly(ferrocenylphosphazene) was formed. The polymer, isolated in 3 5 % yield, has a molecular weight of 950,000. No high polymer is formed without the ferrocenyl group and catalyst. Allcock isn't sure how general this reaction is. But being able to impart ring strain with a transannular metallocene substituent, he says, may work for several other inorganic ring systems "that have so far resisted polymerization under a wide variety of conditions. ' ' Conducting polymer chains formed in zeolite Chemists at the University of New Mexico, Albuquerque, say they have taken "a significant step toward the chemical design of molecular wires," which may be useful in future molecular electronic devices. Patricia Enzel, working with Thomas Bein, has synthesized chains of conducting organic polymers inside the pore systems of zeolite molecular sieves. The zeolite crystals are first ion-exchanged with metal ions
MEETING BRIEFS FROM DALLAS
such as copper(ll) that serve as oxidants in the polymerization reactions. The zeolite pores are dehydrated by heating under vacuum. When the zeolite has returned to room temperature, the monomer, either in solution or in the gas phase, is introduced into the zeolite pores, where it polymerizes. "By using zeolites with different channel topologies," the researchers say, "we can control the arrangement of the conducting polymer chains in the solid host." They have used this method to make polypyrrole, polyaniline, and polythiophene chains. Bein believes the polymer chains are encapsulated inside the zeolite crystals and do not reach to the surface. Tomatoes defend themselves against bugs Damaging a tomato plant triggers enzymatic reactions that inhibit the growth of insects feeding on it, according to entomologist Sean S. Duffey and coworkers at the University of California, Davis. Normally, the enzymes and their targets are separated in the plant tissue. But when cells are damaged, as by insect feeding, the chemicals mix and react. As a result, the insect is less able to digest and assimilate plant proteins. Duffey's studies have focused on proteinase inhibitors, which interfere with insect digestion of protein, and on phenolics, which interact with polyphenol oxidase (PPO) enzymes to bind up the plant protein, again making it less available to the insect. These chemical defenses could lead to insect control methods preferable to synthetic pesticides. However, it won't be simple. One catch, for example, is that the proteinase inhibitors are inactivated by the reaction between PPOs and phenolics. 'Our long-range hope is that molecular biology will enable the transfer of multigene systems to develop these natural defenses in the plant," Duffey says.
scientists currently "use information technologies in very limited ways, if at all," in part because of the widespread use of low-performance terminals with poor user interfaces and low-bandwidth telecommunications lines that drastically restrict the amount of information that can be exchanged with the terminals. Enabling technology for the emerging global information environment of the future, says Smith, includes powerful graphics-oriented workstations, high-bandwidth networks, and application software and windowed operating systems designed with the end user in mind. This technology will accelerate the tendency of scientists to become more personally involved in on-line searching. However, he says, information scientists will become more important than ever as they help end users make full use of these systems. Five-year Ch.E. degree may make comeback The cutting edges of chemical engineering today—biotechnology, new materials, and polymers research—are leading to a reexamination of a five-year degree program, says Larry V. Mclntire, department of chemical engineering chairman at Rice University. Five-year programs were well established until the 1960s, but all schools had switched to four-year programs by the end of that decade. In the 1970s, Mclntire notes, many students were interested in petrochemical processing and energy-related industries. Now, however, "some of the brightest young minds" want to pursue research careers in those "cutting edge" fields. That has created a need for advanced science prerequisites. In addition, "The current four-year system is being challenged by a call for greater attention to ethical, environmental, and safety issues." Mclntire expects opposition to the idea. An alternative, he says, is to split chemical engineering into more specialized areas and streamline the curriculum.
New chemical education newsletter debuts A new publication, the Pan-American Newsletter on ChemicalCatalysts convert hydrocarbons to alcohol Education, will facilitate communication and information Using insights gained from studies of biological enzymes, a exchange in chemical education at all levels among chemical group from the chemistry department of the University of educators throughout the Western Hemisphere. Wayne State California, San Diego, has developed perhalogenated iron University chemical educator Stanley Kirschner, one of the porphyrin catalysts that can efficiently convert hydrocarbons initiators, pointed out to members of the Division of Chemical to industrially useful alcohols at ambient temperature. Many Education that the newsletter is indeed "Pan-American" catalysts now in use not only oxidize hydrocarbons to alcohols, rather than "Latin American," because it's aimed at chemical but also go on to break down the alcohol, making it difficult educators in all the countries of North, Central, and South to stop the process at an intermediate stage. In addition, America. The first issue of the quarterly newsletter contains these catalysts are generally specific to single hydrocarbon articles in English, Spanish, and Portuguese. The editor, substrates and require extreme conditions such as high Guido Canessa C. of the Sociedad Chilena de Quimica, temperatures to function. According to UCSD chemistry invites contributions. professor Teddy G. Traylor and colleagues, the new catalysts "are generalized for various hydrocarbon substrates, and are New technologies to enhance access to data more controllable if you want to stop the process at an intermediate stage. . . . We can convert hydrocarbons to Individual scientists will gain more control over access to alcohols and alkenes to epoxides with . . . high turnover information technologies as sophisticated information systems become increasingly available in coming years. This was the using these agents along with oxygen sources such as message delivered by Dennis H. Smith of Molecular Design hydrogen peroxide." Development of the catalysts emerged Ltd. at the Division of Chemical Information's Herman Skolnik from work in Traylor's lab on the mode of action of proteins Award Symposium. According to Smith, most individual in living systems that contain iron porphyrins. April 24, 1989 C&EN
43
