We report the first
examples of selective and regiodivergent opening
of unsymmetrical phenonium ions with chloride ions. These reactions
are enabled by the dual role of SnCl4 and TiCl4 as Lewis acids and chloride nucleophiles. Reagent control dictates
addition of chloride at either the substituted internal position (SnCl4) or unsubstituted terminal position (TiCl4) of
the phenonium ion. These reactions are highly selective, stereospecific,
operationally simple, and proceed in good to excellent yields. Diverse
product utility is demonstrated.
We report that the treatment of unsymmetrical 2,3-disubstituted aziridines with TiCl 4 yields β-phenethylamine products via the intermediacy of a phenonium ion. Derivatization of the products obtained via this method is demonstrated. Computational analysis of the reaction pathway provides insight into the reaction mechanism, including the selectivity of the phenonium opening.
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.1 Introduction2 Select Examples of Phenonium Ion Methodology3 Regiodivergent Opening of Nonsymmetrical Phenonium Ions4 Summary and Outlook
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.