1
6 WWW.CEN-ONLINE.ORG JANUARY 12, 2009 R RR X RX + Fe(MgX) 2 X = Cl, Br T HE UNITED NATIONS General Assembly has passed a resolution formally declaring 2011 as the International Year of Chemistry. Ethiopia, which is the host country for the Federation of African Societies of Chemistry, submitted the resolution calling for the year, which will highlight the achievements of chemistry and its contributions to humanity. “The International Year of Chem- istry will give a global boost to chemi- cal science in which our life and our future are grounded,” says Jung-Il Jin, president of the International Union of Pure & Applied Chemistry (IUPAC) and a professor of chemistry at Korea University, in Seoul, South Korea. “We hope to increase the public appreciation and understanding of chemistry, increase young people’s interest in science, and generate en- thusiasm for the creative future of chemistry,” he adds. IUPAC has established a management panel that will work with chemical societies; the UN Educational, Sci- entific & Cultural Organization (UNESCO); and others to plan and implement activities during the year. “We are delighted that Ethiopia has provided inter- national leadership to bring this forward, first to the UNESCO executive board and then to the UN General Assembly this fall,” says Peter Mahaffy, professor of chemistry at King’s University College, in Edmonton, Alberta, and chair of IUPAC’s Committee on Chemistry Education. The UN resolution, he says, was formally sponsored by more than 35 countries and supported by many oth- ers. “The American Chemical Society and the National Academy of Sciences both played a very helpful role in winning support in the U.S.,” Mahaffy notes. “This designation by the United Nations is truly exciting,” ACS President Thomas H. Lane says. “It is an opportunity for our world to learn more about the transforming powers of chemistry.” Lane says ACS will make its expertise, networks, and National Chemistry Week experience available to help ensure a successful year. “Further,” he adds, “we will help provide opportunities for Nobel Laureates, eminent scientists, teachers, outstanding young chem- istry students, and chemistry communities around the world to demonstrate how people’s lives are improved through chemistry.”—GLENN HESS D IRECT CROSS-COUPLING of aryl halides with alkyl halides to form substituted aryl com- pounds—one of the most indispensable types of reactions in organic synthesis—has just gotten easi- er thanks to a new procedure that combines the forma- tion of Grignard reagents and iron catalysis in one-pot reactions (Angew. Chem. Int. Ed. 2009, 48, 607). The approach, designed by Waldemar M. Czaplik, Matthias Mayer, and Axel Jacobi von Wangelin of the University of Cologne, in Germany, builds on previ- ous iron-mediated Grignard cross-coupling methods. But rather than separately preforming large amounts of hazard- ous organomagnesium reagents, as in standard Grignard coupling reactions, the new se- quence forms Grignard reagents in situ. It also avoids the higher cost and toxicity problems associated with palladium and nickel cross-coupling catalysts. For a typical reaction, the researchers add FeCl 3 dis- solved in tetrahydrofuran to a flask containing magne- sium turnings. They also add tetramethylethylenediamine to serve as a ligand for stabilizing organometallic inter- mediates. They then add aryl and alkyl bromide reagents and allow the reaction to run for three hours at 0 ºC before quenching it and isolating the product. Iron catalyzes the in situ formation of the Grignard reagents, Jacobi von Wangelin explains. Although the exact details aren’t yet known, it appears that alkyliron and arylmagnesium species are at work, he says. As these reagents form, the active cross-coupling catalyst, which the researchers believe is Fe(MgX) 2 , where X is Cl or Br, also forms. The team used a variety of aryl-alkyl and alkenyl-alkyl combinations to make coupling products with up to 81% yield. Slow formation of the Grignard reagents combined with the rapid iron-catalyzed coupling step keeps the con- centration of reactive organomagnesium intermediates low throughout the reaction, Jacobi von Wangelin says. This approach to aryl-alkyl cross-couplings “nicely illustrates a general trend in today’s catalytic organic chemistry: to achieve high selectivity with simple, readily available reagents in a safe and environmentally benign manner,” notes Carsten Bolm of RWTH Aachen Universi- ty, in Germany. The Cologne team’s reaction is effectively “cross-coupling made easy,” Bolm says.—STEVE RITTER NEWS OF THE WEEK CROSS-COUPLING MADE EASY ORGANIC SYNTHESIS: Iron catalysis simplifies coupling of aryl and alkyl Grignard reagents 2011, INTERNATIONAL YEAR OF CHEMISTRY COMMEMORATION: United Nations will celebrate chemistry SHUTTERSTOCK

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6WWW.CEN-ONLINE.ORG JANUARY 12, 2009

R

R′

R

X

R′ X

+

Fe(MgX)2

X = Cl, Br

THE UNITED NATIONS General Assembly has passed a resolution formally declaring 2011 as the International Year of Chemistry. Ethiopia,

which is the host country for the Federation of African Societies of Chemistry, submitted the resolution calling

for the year, which will highlight the achievements of chemistry and its contributions to humanity.

“The International Year of Chem-istry will give a global boost to chemi-cal science in which our life and our future are grounded,” says Jung-Il Jin, president of the International Union of Pure & Applied Chemistry (IUPAC) and a professor of chemistry at Korea University, in Seoul, South Korea.

“We hope to increase the public appreciation and understanding of chemistry, increase young people’s interest in science, and generate en-

thusiasm for the creative future of chemistry,” he adds.IUPAC has established a management panel that will

work with chemical societies; the UN Educational, Sci-entific & Cultural Organization (UNESCO); and others to plan and implement activities during the year.

“We are delighted that Ethiopia has provided inter-national leadership to bring this forward, first to the UNESCO executive board and then to the UN General Assembly this fall,” says Peter Mahaffy, professor of chemistry at King’s University College, in Edmonton, Alberta, and chair of IUPAC’s Committee on Chemistry Education.

The UN resolution, he says, was formally sponsored by more than 35 countries and supported by many oth-ers. “The American Chemical Society and the National Academy of Sciences both played a very helpful role in winning support in the U.S.,” Mahaffy notes.

“This designation by the United Nations is truly exciting,” ACS President Thomas H. Lane says. “It is an opportunity for our world to learn more about the transforming powers of chemistry.”

Lane says ACS will make its expertise, networks, and National Chemistry Week experience available to help ensure a successful year. “Further,” he adds, “we will help provide opportunities for Nobel Laureates, eminent scientists, teachers, outstanding young chem-istry students, and chemistry communities around the world to demonstrate how people’s lives are improved through chemistry.”—GLENN HESS

DIRECT CROSS-COUPLING of aryl halides with alkyl halides to form substituted aryl com-pounds—one of the most indispensable types

of reactions in organic synthesis—has just gotten easi-er thanks to a new procedure that combines the forma-tion of Grignard reagents and iron catalysis in one-pot reactions (Angew. Chem. Int. Ed. 2009, 48, 607).

The approach, designed by Waldemar M. Czaplik, Matthias Mayer, and Axel Jacobi von Wangelin of the University of Cologne, in Germany, builds on previ-

ous iron-mediated Grignard cross-coupling methods.

But rather than separately preforming large amounts of hazard-

ous organomagnesium reagents, as in standard Grignard coupling reactions, the new se-quence forms Grignard reagents in situ. It also avoids the higher cost and toxicity problems associated

with palladium and nickel cross-coupling catalysts.For a typical reaction, the researchers add FeCl3 dis-

solved in tetrahydrofuran to a flask containing magne-sium turnings. They also add tetramethylethylenediamine to serve as a ligand for stabilizing organometallic inter-mediates. They then add aryl and alkyl bromide reagents and allow the reaction to run for three hours at 0 ºC before quenching it and isolating the product.

Iron catalyzes the in situ formation of the Grignard reagents, Jacobi von Wangelin explains. Although the exact details aren’t yet known, it appears that alkyliron and arylmagnesium species are at work, he says. As these reagents form, the active cross-coupling catalyst, which the researchers believe is Fe(MgX)2, where X is Cl or Br, also forms.

The team used a variety of aryl-alkyl and alkenyl-alkyl combinations to make coupling products with up to 81% yield. Slow formation of the Grignard reagents combined with the rapid iron-catalyzed coupling step keeps the con-centration of reactive organomagnesium intermediates low throughout the reaction, Jacobi von Wangelin says.

This approach to aryl-alkyl cross-couplings “nicely illustrates a general trend in today’s catalytic organic chemistry: to achieve high selectivity with simple, readily available reagents in a safe and environmentally benign manner,” notes Carsten Bolm of RWTH Aachen Universi-ty, in Germany. The Cologne team’s reaction is effectively “cross-coupling made easy,” Bolm says.—STEVE RITTER

NEWS OF THE WEEK

CROSS-COUPLING MADE EASY

ORGANIC SYNTHESIS: Iron catalysis simplifies coupling of aryl and

alkyl Grignard reagents

2011, INTERNATIONAL YEAR OF CHEMISTRYCOMMEMORATION: United Nations

will celebrate chemistry

SHUTTERSTOCK