Activation of the dienophilicity of indoles in normal electron demand [4 + 2] cycloadditions under high pressure

reaction: see Text] Activation by either high pressure or a combination of Lewis acid catalysis and high pressure allows indole derivatives to behave as dienophiles in 4 + 2] cycloaddition reactions under mild conditions. The biactivation mode has the highest impact on the stereoselectivity of the reaction. The cycloadducts resulting from these reactions are characterized by boat-shape conformations that bear well-defined orthogonal planes.