A new concept in organocatalysis allowing for the construction of cyclobutanes with four contiguous stereocenters with complete diastereo- and enantiomeric control by a formal [2 + 2]-cycloaddition is presented. The concept is based on simultaneous dual activation of α,β-unsaturated aldehydes and nitroolefins by amino- and hydrogen-bonding catalysis, respectively. A new bifunctional squaramide-based aminocatalyst has been designed and synthesized in order to enable such an activation strategy. The potential and scope of the reaction are demonstrated, and computational studies which account for the stereochemical outcome are presented.

Right direction: The presented enantioselective strategy for the preparation of diversely functionalized tetrahydroxanthones is based on a trienamine-mediated cycloaddition between 2,4-dieneals and activated chromones. It is possibile to control the stereochemical outcome of such reactions by employing an H-bond-directing aminocatalyst.

In die richtige Richtung: Die vorgestellte enantioselektive Synthese von funktionalisierten Tetrahydroxanthonen basiert auf einer Trienamin‐vermittelten Cycloaddition zwischen 2,4‐Dienalen und aktivierten Chromonen. Die Kontrolle des stereochemischen Ausgangs der Reaktion wird durch Einsatz eines H‐Brücken‐dirigierenden Aminokatalysators ermöglicht.

Diversely functionalized tetrahydroxanthones are prepared from 2,4‐dienals and activated 3‐cyanochromones via a [4+2] cycloaddition reaction catalyzed by squaramide‐based catalyst SQA.

Rational catalyst design supported by computational studies enables the development of a new dual activation mode for the synthesis of fully substituted cyclobutanes with complete diastereo‐ and enantioselectivity.