Addition of Transiently-Generated Methyl o-Lithiobenzoate to Imines. An Isoindolone Annulation

Addition of phenyllithium to a mixture of an imine, methyl o-iodobenzoate, and BF(3).etherate at -105 degrees C gives good to excellent yields of isoindolones. The transient formation of methyl o-lithiobenzoate is proposed, which is formed by a rapid lithium/iodide exchange reaction of the phenyllithium with methyl o-iodobenzoate in the presence of the imine. The transiently generated anions can then be captured by the BF(3)-activated imines to form the isoindolones in good to high yield. The reactions conditions are sufficiently mild, and selective, to permit functional groups such carbmethoxy and aryl bromide, which could otherwise react with the added PhLi, to be tolerated.