Triethylamine (3.0 equivalents), potassium vinyltrifluoroborate (1.0 equivalent) and dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium (II) dichloromethane adduct (0.2 equivalent) were added to a solution of 7-bromo-1-(2-methylpropyl)-2-propyl-1H-imidazo[4,5-c]quinolin-4-amine (1.0 equivalent) in n-propanol (30 ml/g). The reaction mixture was heated at reflux under a nitrogen atmosphere until it was complete (between four and 18 hours) and then poured into water (3 volumes). The pH of the mixture was monitored and adjusted to pH 12 with the addition of 10% aqueous sodium hydroxide if needed. The mixture was extracted with ethyl acetate, and the combined organic fractions were filtered and concentrated under reduced pressure. The crude product was purified by flash column chromatography on silica gel (eluting with chloroform:methanol in a gradient from 100:0 to 90:10), followed by recrystallization from acetonitrile to provide 1-(2-methylpropyl)-2-propyl-7-vinyl-1H-imidazo[4,5-c]quinolin-4-amine as an off-white solid.
