NEWS OF THE W EEK
HECK REACTION GOES SILYL
tion, but it just got in the way, preventing the reaction, Watson explained. Eventually, his group found a ligand that was not too big and not too small: tert-butyldiphenylphosphine. With their ligand now just right, they modified the reaction conditions to use the silane source ACS MEETING NEWS: Ligand chlorotrimethylsilane in place of iodoenables silicon variant of familiar trimethylsilane because the former sells palladium-catalyzed chemistry for a fraction of the price (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201200060). “It is surprising that this reaction has not been What’s most interesting about developed before now.” Y DESIGNING a “goldilocks” catalyst—one the new method is that it generates —EDWARD A. ANDERSON, with just the right balance of size and electron- a trimethylsilylmetal intermediate OXFORD UNIVERSITY donating properties—University of Delaware that could be broadly useful, Scott E. chemists have added a new reaction to the tool kit for Denmark, an expert in organosilicon chemistry at the forming carbon-silicon bonds. University of Illinois, Urbana-Champaign, told C&EN. The process converts alkenes, which are easily accessi- Although the compounds the team reported can be ble starting materials, to vinylsilanes and allylsilanes, re- made in other ways, the researchers “have an opportuagents with applications in several branches of synthesis. nity for making an impact on other less readily available Donald A. Watson, who silanes,” he said. led the research, presentIt’s possible the JUST RIGHT The silyl-Heck reaction converts ed the work last week at method could even be carbon-hydrogen bonds to carbon-silicon bonds. the American Chemical applied to polymers such Society’s national meetas silicones, added Miing in San Diego. chael A. Brook, an expert Chemists already in materials chemistry of have ways of obtaining silicon at McMaster Uniallylsilanes and vinylsiversity, in Ontario. lanes, “but they’re not easy to make, and they tend to In San Diego, Watson mentioned that his team is require harsh conditions,” Watson told C&EN. Buildworking toward an X-ray structure of their trimethyling on the work of other researchers, Watson, graduate silylmetal intermediate, which he said will help them students Jesse R. McAtee and Sara E. S. Martin, and col- further optimize reaction conditions. leagues set out to develop a mild, palladium-catalyzed “This is a creative piece of work,” said Edward A. Anreaction that would convert the C–H bond of an alkene derson, who studies vinylsilanes at Oxford University. to a C–Si bond, analogous to the Nobel Prize-winning He cautions that the reaction’s current need for excess Heck reaction, which converts those C–H bonds to silane might limit its application to highly functionalC–C bonds. ized substrates. However, the Delaware team’s search The group’s first attempts didn’t work, but they even- for the best ligand “showed great insight,” he added. “It tually realized that the problem was a bulky ligand on is surprising that this reaction has not been developed their catalyst. It provided much-needed electron dona- before now.”—CARMEN DRAHL
B
LAWSUIT Court directs FDA to finalize ruling on antibiotics for animal growth promotion A federal judge has ordered the Food & Drug Administration to stop antibiotics from being used to fatten up foodproducing animals, unless such practice can be proven safe. The decision comes in response to a lawsuit filed last May by the Natural Resources Defense Council and other advocacy groups that believe excessive use of antibiotics in farm animals contributes to a rise in antibioticresistant bacteria, thereby threatening human health. The lawsuit alleged that FDA acted illegally by not following through with its 1977 proposal to ban the use of penicillin
and the tetracycline class of antibiotics for promoting growth in livestock. At that time, FDA said such uses could not be shown to be safe. But “FDA never held hearings or took any further action on the proposed withdrawals,” U.S. Magistrate Judge Theodore H. Katz wrote in his March 22 decision. “In the intervening years, the scientific evidence of the risks to human health from the widespread use of antibiotics in livestock has grown, and there is no evidence that the FDA has changed its position,” Katz said. Katz directed FDA to prohibit the ad-
WWW.CEN-ONLIN E .ORG
9
AP RI L 2, 20 1 2
dition of penicillin and tetracyclines to animal feed for growth promotion, unless drug manufacturers can provide evidence at a public hearing that such uses are safe. The antibiotics can still be used, however, for disease treatment and prevention in livestock. Rep. Louise M. Slaughter (D-N.Y.), who has long pressured FDA to address overuse of antibiotics in farm animals, applauded the ruling. “This is a good first step,” she said, “but to really get in front of this problem we must address all classes of antibiotics in farm animals.”— BRITT ERICKSON
