Revisiting the 'Phenonium Phenomenon': Regiodivergent Opening of Nonsymmetrical Phenonium Ions with Halide Nucleophiles

Formation of phenonium ions through anchimeric assistance (neighboring-group participation) of aryl rings has been known since 1949. Although these reactive intermediates have been studied extensively by physical organic chemists, their potential as control elements in synthesis is underutilized. Presented here are our laboratory's recently reported first examples of regiodivergent openings of nonsymmetrical phenonium ions with chloride nucleophiles. The selectivity of these processes is under reagent control. The reactions are operationally simple and permit the stereospecific synthesis of complex chiral building blocks from readily accessible epoxide starting materials.

Automated summary

Phenonium ions can be formed through neighboring-group participation of aryl rings, and can undergo regiodivergent openings with chloride nucleophiles. The selectivity of these reactions is controlled by the reagents, allowing for the stereospecific synthesis of complex chiral building blocks from readily accessible epoxide starting materials.