12WWW.CEN-ONLINE.ORG NOVEMBER 2, 2009

F ULLERENES can catalyze hydrogenation of organic compounds as eff ectively 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 eff ects of

heavy-metal pollutants. Transition-metal catalysts lie at

the heart of global-scale hy-drogenation processes, such

as the ones used to refine crude oil and to synthesize the common fertilizer ammonia. Nonmetal hydroge-nation catalysts could provide industry with substan-tial cost savings. But such catalysts typically require high temperatures and pressures or are ineffective at mediating hydrogenations with molecular hydrogen;

NO2

NH2

+ H2

EACH SET of building blocks for life on Earth has a signature handedness, and researchers have speculated that circularly polarized light (CPL)

from outer space is one potential source of that unifor-mity. Inspired by that possibility, Dutch researchers have demonstrated its feasibility by combining CPL and me-chanical grinding to determine the chiral fate of a small molecule ( Nat. Chem., DOI: 10.1038/nchem.416).

The team believes the work has implications for origin-of-life research studies and could lead to a better understanding of how organic molecules in-teract with light.

Shining CPL, which corkscrews either left or right, on an equal mixture of a chiral mol-ecule’s two mirror-image forms generates a tiny excess of one form, or enantiomer. Researchers have previously amplified that CPL-generated imbalance to obtain a pure sample of one enantiomer. However, the process is far from systematic.

Noorduin adjusts a CPL irradiation apparatus.

Irradiating nitrobenzene in the presence of a fullerene catalyst yields nearly 100% aniline.

NEWS OF THE WEEK

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SPARKINGA SIGN OF LIFE

CRYSTAL GROWTH: Specialized light source drives formation of

optically pure amino acid derivatives

HYDROGENATION WITHOUT METALS

CATALYSIS: Fullerenes drive nitro-to-amino conversion of

aromatics under mild conditions

Now, Wim L. Noorduin and Elias Vlieg of Radboud University, in Nijmegen; Bernard Kaptein of DSM Phar-maceutical Products, in Geleen; Richard M. Kellogg of contract research company Syncom, in Groningen; and coworkers have achieved chiral resolution by pairing CPL with a chiral amplification method they devel-oped previously. The earlier method induces chirality by combining a base, which causes interconversion between enantiomers in solution, with abrasive grind-ing of a suspension of crystals, reminiscent of crashing waves on the rocks or sand of a primitive Earth.

The team exposed racemic crystal mixtures of an amino acid derivative to CPL and then initiated grind-ing. They obtained chirally pure crystals of either enantiomer on demand, with the rotation sense of the light determining the chirality of the product.

Their results suggest that CPL initially generates a chiral product that selectively blocks crystallization of one of the enantiomers. Identifying that product will be a key next step, Vlieg says.

“CPL photochemistry certainly provides a feasible mechanism to get homochiral amino acids under prebiotic conditions, and this work provides an experimental demon-stration of at least part of such a scenario,” says Ben L. Feringa, who explores chirality’s origins at the University of Groningen, also in the Netherlands. —CARMEN DRAHL

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 ni-trobenzene containing a small quantity of C 60 , while irradiating the reagents with ultraviolet light, yields aniline in nearly 100% yield. That level of catalytic per-formance 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 C 60 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 C 70 gives similar results.

“These results are quite interesting” and are likely to catch the attention of researchers in many fields, in-cluding green chemistry, says Yoshiaki Nishibayashi, a chemistry professor at the University of Tokyo. The ex-act role of the fullerenes remains unclear and needs to be explored for further development of new catalysts, he adds. —MITCH JACOBY

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Amino acid derivative