Functionalization of saturated hydrocarbons: 3. One-step alkylacylation of aromatic hydrocarbons with alkanes (or cycloalkanes) in the presence of aprotic organic superacids

Alkanes and cycloalkanes (isobutane, butane, isopentane, isohexane, and methylcyclopentane) react with benzene or bromobenzene at 0–20 °C in the presence of RCO+Al2X7− complexes (R=Me, Pr, or Ph; X=Cl or Br) to give products of the alkylacylation of arenes. The yields of alkylated aromatic ketones reach 60–87 % in 5–30 min, whereas the yields of unalkylated aromatic ketones (the competitive reaction) reach 0–40 %. The reactions of isobutane or isopentane with benzene result exclusively inpara isomers oft-BuC6H4COR or a mixture of Me2(Et)CC6H4COR and Me(i-Pr)CHC6H4COR isomers (1∶1), respectively. The reaction of isobutane with benzene also proceeds regioselectively and gives only one isomer, 2-Br-t-BuC6H4COR.