Issue Date: September 19, 2011
Rule breaking Leads to Primary Alcohols …
By linking three processes in one pot, chemists have taken a step toward a greener alternative to hydroboration/oxidation, the classic two-step method for forming primary alcohols from alkenes (Science, DOI: 10.1126/science.1208685). Obtaining primary alcohols through hydroboration requires stoichiometric amounts of reagents. To find a catalytic alternative, Caltech’s Robert H. Grubbs, Guangbin Dong, Peili Teo, and Zachary K. Wickens had to override Markovnikov’s rule, which dictates that a proton should end up on the less substituted alkene carbon, forming a secondary alcohol instead of the desired primary alcohol. Their approach is a catalysis triple-header, beginning with an unusual palladium-mediated oxidation of an alkene to an aldehyde, followed by acid-catalyzed hydrolysis and reduction with a ruthenium catalyst, yielding a primary alcohol. So far, the procedure works best on styrenes, and it requires relatively high catalyst loadings and stoichiometric amounts of benzoquinone. Dong, now an assistant professor at the University of Texas, Austin, says Grubbs’s team is designing new catalysts and optimizing conditions to eliminate those limitations and make the method cost-competitive with hydroboration.
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