High diastereoselective [4 + 2] annulation of β,γ-unsaturated α-keto esters and p-quinone methides: Approach to polysubstituted 4-aryl chromans and tetrahydroquinolines

Abstract DBU-mediated [4 + 2] annulation of β,γ-unsaturated α-keto esters and p-quinone methides has been developed. Under mild conditions, the reaction afforded polysubstituted 4-aryl chromans and tetrahydroquinolines as single diastereoisomer in high yields (up to 91% yield) at room temperature.