Antagonistic Catalyst Turns Tandem Reaction | Chemical & Engineering News
Volume 89 Issue 38 | p. 29 | Concentrates
Issue Date: September 19, 2011

Antagonistic Catalyst Turns Tandem Reaction

Controlled installation of acidic and basic functional groups on silica produces a two-in-one catalyst
Department: Science & Technology
Keywords: bifunctional catalyst, acid catalyst, base catalyst, polyoxometallate, heterogeneous catalysis
Amine groups and phosphotungstate groups on silica provide antagonistic catalytic activity.
Amine groups
Amine groups and phosphotungstate groups on silica provide antagonistic catalytic activity.

Chemists have succeeded in mimicking antagonistic acid and base catalytic functions observed in some enzymes by synthesizing a dual-purpose heterogeneous catalyst capable of carrying out one-pot tandem reactions (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201101449). Soluble homogeneous catalysts that combine chemically hostile functional groups have been made successfully, but synthesizing similar bifunctional solid catalysts “is no easy task,” saysGadi Rothenberg of the University of Amsterdam, who led the research team with colleague N. Raveendran Shiju. The trick, Rothenberg says, is to install the acid and base groups far enough apart so they don’t neutralize each other. To accomplish that, the researchers first grafted propylamine groups, –(CH2)3NH2, onto mesoporous silica and then immobilized phosphotungstate groups, –(CH2)3NH3[H2PW12O40], on half of the amines. The team tested the catalyst by converting dimethoxymethylbenzene to trans-1-nitro-2-phenylethylene. The tandem reaction begins with an acid-catalyzed de­acetalization to form benzaldehyde, followed by a base-catalyzed Henry reaction with nitromethane to give the nitro product. The catalyst could be used for multiple types of reactions, Rothenberg adds, noting that it can be made primarily acidic, primarily basic, or equally acidic and basic by controlling the acid:base active-site ratio.

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