Phenyldiazenes from Phenyl Diazonium Fluoborate and Carbanions

Abstract

The lack of efficient methods to aminate carbanions (R-Metal to RNH₂) limits the strategies for alkaloid synthesis. Among the various electrophilic nitrogen reagents used to effect this transformation, chloramine,^1a hydroxylamine-0-mesitylsulfonate, nitrosyl chloride^lc and tosyl azide^1c are the most popular, each affording useful yields of the desired transformation in selected instances. We reasoned that an ideal electrophilic nitrogen agent should react by addition to an unsaturated nitrogen (à la tosyl azide) rather than by displacement of a leaving group at an electron rich center (chloramine). Further, the carbanion-nitrogen adduct should be relatively stable needing minimal manipulations to the desired amine in contrast with nitrosyl chloride. Diazonium ions and nitroso compounds seemed to have these properties; we report here observations concerning the reactions of Grignards and enolates with phenyldiazonium fluoborate.²