NEWS OF THE WEEK
DICK VAN AALST/RADBOU D U N IVERSIT Y
SPARKING A SIGN OF LIFE
Noorduin adjusts a CPL irradiation apparatus.
Now, Wim L. Noorduin and Elias Vlieg of Radboud University, in Nijmegen; Bernard Kaptein of DSM Pharmaceutical Products, in Geleen; Richard M. Kellogg of contract research company Syncom, in Groningen; and coworkers have achieved chiral resolution by pairing CRYSTAL GROWTH: Specialized light CPL with a chiral amplification method they develsource drives formation of oped previously. The earlier method induces chirality optically pure amino acid derivatives by combining a base, which causes interconversion between enantiomers in solution, with abrasive grinding of a suspension of crystals, reminiscent of crashing ACH SET of building blocks for life on Earth has waves on the rocks or sand of a primitive Earth. a signature handedness, and researchers have The team exposed racemic crystal mixtures of an speculated that circularly polarized light (CPL) amino acid derivative to CPL and then initiated grindfrom outer space is one potential source of that uniforing. They obtained chirally pure crystals of either mity. Inspired by that possibility, Dutch researchers have enantiomer on demand, with the rotation sense of the demonstrated its feasibility by combining CPL and melight determining the chirality of the product. chanical grinding to determine the chiral fate of a small Their results suggest that CPL initially generates a molecule (Nat. Chem., DOI: 10.1038/nchem.416). chiral product that selectively blocks crystallization of The team believes the work has implications for one of the enantiomers. Identifying that product will be origin-of-life research studies and could lead to a better a key next step, Vlieg says. understanding of how organic molecules in“CPL photochemistry certainly teract with light. provides a feasible mechanism to Shining CPL, which corkscrews either left get homochiral amino acids under or right, on an equal mixture of a chiral molprebiotic conditions, and this work ecule’s two mirror-image forms generates provides an experimental demonH2N a tiny excess of one form, or enantiomer. stration of at least part of such a N O Researchers have previously amplified that scenario,” says Ben L. Feringa, who CPL-generated imbalance to obtain a pure explores chirality’s origins at the sample of one enantiomer. However, the University of Groningen, also in Amino acid derivative process is far from systematic. the Netherlands.—CARMEN DRAHL
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HYDROGENATION WITHOUT METALS CATALYSIS: Fullerenes drive nitro-to-amino conversion of aromatics under mild conditions
F + H2 NO2
Irradiating nitrobenzene in the presence of a fullerene catalyst yields nearly 100% aniline.
ULLERENES can catalyze hydrogenation of
organic compounds as effectively as metals can, according to a study by researchers in China (J. Am. Chem. Soc., DOI: 10.1021/ja9061097). The discovery may lead to replacing precious-metal catalysts with carbon-based substitutes, which could reduce costs and the environmental effects of heavy-metal pollutants. Transition-metal catalysts lie at the heart of global-scale hyNH2 drogenation processes, such as the ones used to refine crude oil and to synthesize the common fertilizer ammonia. Nonmetal hydrogenation catalysts could provide industry with substantial cost savings. But such catalysts typically require high temperatures and pressures or are ineffective at mediating hydrogenations with molecular hydrogen; WWW.CEN-ONLINE.ORG
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they work instead with other hydrogen sources. Now, Nanjing University chemists Baojun Li and Zheng Xu report that nitroaromatic compounds are readily and selectively hydrogenated to aromatic amines by molecular hydrogen under mild conditions in the presence of a fullerene catalyst. Specifically, the team finds that bubbling hydrogen at atmospheric pressure through a room-temperature solution of nitrobenzene containing a small quantity of C60, while irradiating the reagents with ultraviolet light, yields aniline in nearly 100% yield. That level of catalytic performance is considered the hallmark of noble metals such as palladium and platinum. The reaction runs well without UV radiation but requires higher temperature and pressure, the team notes. For example, a 2:1 mixture of neutral and anionic forms of C60 also leads to nearly 100% yield of aniline but requires raising the temperature above 120 °C and the pressure to about 4 megapascals. The group reports that C70 gives similar results. “These results are quite interesting” and are likely to catch the attention of researchers in many fields, including green chemistry, says Yoshiaki Nishibayashi, a chemistry professor at the University of Tokyo. The exact role of the fullerenes remains unclear and needs to be explored for further development of new catalysts, he adds.—MITCH JACOBY
NOV E M BE R 2 , 20 0 9
