Lewis Acid Regulated Divergent Catalytic Reaction between Quinone Imine Ketals (QIKs) and 1,3-Dicarbonyl Compounds: Switchable Access to Multiple Products Including 2-Aryl-1,3-Dicarbonyl Compounds, Indoles, and Benzofurans

A catalytic Lewis acid regulated reaction between quinone imine ketals (QIKs) and 1,3-dicarbonyl compounds provides a divergent and tunable approach to a variety of skeletons, including a series of 2-aryl-1,3-dicarbonyl compounds, indoles, and benzofurans. The use of lithium chloride and ferrous bromide gives C3- or C2-alkylation products of the QIKs. The combination of ferrous bromide and trifluoromethanesulfonic acid delivers indole derivatives. Sequential hydrolysis and C3-alkylation occur in the presence of ytterbium (III) trifluoromethanesulfonate and stoichiometric amounts of water. When the reaction is performed with trifluoromethanesulfonic acid and stoichiometric amounts of water, benzofuran is obtained. This protocol utilizes mild conditions, exhibits regio- and chemoselectivity, and has broad functional group tolerance.