A stereoselective annulation protocol was developed to construct dihydrofuranoindoles from readily available starting materials. In the presence of a bifunctional squaramide, the Friedel−Crafts alkylation/annulation cascade process occurred smoothly to provide dihydrofuranoindoles in 26−95% isolated yields exclusively as trans-diastereomers (38−99% ee). This catalytic protocol was compatible with a range of structurally distinct hydroxyindoles bearing the hydroxyl group at different positions, providing four kinds of dihydrofuranoindoles. Moreover, gram-scale synthesis and further synthetic manipulation of the product were also demonstrated.
A triple Michael/aldol cascade reaction has been established to construct tetracyclic chromanes in a diastereoselective fashion (≥5:1 dr). The polycyclic products were generated in 50-78% isolated yields under mild and...
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