Selective Generation of Lithiated Benzonitriles: the Importance of Reaction Conditions

Lithiated benzonitriles can be generated in high yields from reactions of bromobenzonitriles with n-BuLi in THF under standard cryogenic conditions (ca. −70 °C) provided the reverse addition mode is employed. The resultant aryllithiums are fairly stable at temperatures up to −60 °C. The formation of lithiated benzonitriles via Br/Li exchange under normal addition mode conditions is plagued by deprotonation and extensive CN-addition reactions. The generation of related aryllithiums from disilylated bromobenzonitriles is comparatively less sensitive to reaction conditions.