Friedel-Crafts Reaction of Indole Derivatives Using the Iminium Salt Generated by the Oxidation of Amino Ketene Silyl Acetal

Friedel-Crafts reaction of various indole derivatives proceeded with the iminium salt generated by the oxidation of amino ketene silyl acetal to give the addition products in good yields.Further reaction of the introduced glycine moiety of the adducts with the second nucleophiles provided double nucleophilic addition products.Intriguing reactivity of the iminim salts generated by the oxidation of aluminum enolate derivatives has enabled the use of α-imino esters as acceptors of two nucleophiles (eq 1). 1 Generation of iminium species by the oxidation of the intermediary enolates was extended to the use of amino ketene silyl acetal, readily isolable enolate derivatives as starting materials, and this methodology offers a simple approach to a variety of α-amino esters in a short step (eq 2).