Adding Metals To Toluene

Mixed-metal reagents can be tuned to selectively create metal-carbon bonds in toluene at 2,5 or 3,5 positions, depending on the identity of an alkyl component, says a group of researchers led by Robert E. Mulvey of the University of Strathclyde, in Scotland (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200801158). The dimetalated products can be treated further to create other aromatic compounds. Traditionally, chemists have metalated aromatic compounds by using organolithium reagents to form lithium-carbon bonds, then reacting the products with metal salts. In the new approach, Mulvey and colleagues used sodium manganese or sodium magnesium compounds to directly create C–Mn or C–Mg bonds. They found that reacting [Na(n-butyl)(tmp)Mg(tmp)] (tmp = 2,2,6,6-tetramethylpiperidide) with toluene led to substitution at the 2 and 5 ring positions. When they replaced the n-butyl component of the reagent with CH₂Si(CH₃)₃, the resulting product was substituted at the 3 and 5 positions. Screening similar compounds with varying ligand combinations could lead to new reagents with different specificities, the authors say.