Environment guides reactions

Catalytic reactions can be steered in unusual directions by controlling the catalyst's chemical environment, according to a study conducted at the University of California, Berkeley. Alexander Katz, John D. Bass, and coworkers have shown that by immobilizing primary amines on silica and surrounding the catalytic amine groups with cyano groups, the Henry reaction-a C-C bond-forming reaction that couples aldehydes and nitroalkanes and ordinarily forms olefin products using primary amine catalysts-can instead be used to prepare alcohols with high selectivity (J. Am. Chem. Soc., published online Feb. 24, dx.doi.org/10.1021/ja057395c). The group explains that in the presence of native silanol (SiOH) groups, the reaction forms olefins by way of an acid-base mechanism. In contrast, the polar, aprotic environment associated with cyano groups guides the reaction to produce alcohols via an ion-pair mechanism that was postulated previously for primary amine catalysts but not verified experimentally until now.