Catalytic intramolecular crossed aldehyde--ketone benzoin reactions: a novel synthesis of functionalized preanthraquinones.

Stereochemically and functionally rich polycyclic compounds are obtained by the first crossed aldehyde-ketone benzoin reaction in excellent yield under mild reaction conditions (5-20 mol % thiazolium salt, 10-70 mol % DBU, tBuOH, 40 degrees C, 30 min). This novel catalytic methodology offers a convenient approach to sophisticated molecular architectures useful for the stereocontrolled construction of polycyclic compounds as well as the fully regiocontrolled synthesis of anthra- and naphthoquinones.