Nucleophilic Capture of Unsymmetrical Oxyallyl Cations with Indoles under Mild Bronsted Acid Catalysis

We recently reported a new synthetic method in our laboratory concerning the control of regioselectivity in the addition of nucleophiles, such as indoles, to unsymmetrical oxyallyl cations. These reactive intermediates were readily generated upon ionization of the corresponding α-hydroxy enol ether precursors under catalytic, mild Bronsted acid. Results from our expansive scope of substrate studies revealed that regioselectivity in this reaction could be regulated upon protection of the oxygen atom in the oxyallyl cation moiety as well as modulation of the stereoelectronic effects in the participating α vs. α′ substituents.