Directing the Activation of Donor–Acceptor Cyclopropanes Towards Stereoselective 1,3‐Dipolar Cycloaddition Reactions by Brønsted Base Catalysis

The first stereoselective organocatalyzed [3+2] cycloaddition reaction of donor‐acceptor cyclopropanes is presented. It is demonstrated that by applying an optically active bifunctional Brønsted base catalyst, racemic di‐cyano cyclopropylketones can be activated to undergo a stereoselective 1,3‐dipolar reaction with mono‐ and polysubstituted nitroolefins. The reaction affords functionalized cyclopentanes with three consecutive stereocenters in high yield and stereoselectivity. Based on the stereochemical outcome, a mechanism in which the organocatalyst activates both the donor‐acceptor cyclopropane and nitroolefin is proposed. Finally, chemoselective transformations of the cycloaddition products are demonstrated. Eine [3+2]‐Cycloaddition nutzt eine optisch aktive difunktionelle Brønsted‐Base als Katalysator, um racemische Dicyancyclopropylketone für stereoselektive 1,3‐dipolare Reaktionen mit mono‐ und polysubstituierten Nitroolefinen zu aktivieren. Als Produkte dieses stereoselektiven organokatalytischen Prozesses entstehen funktionalisierte Cyclopentane mit drei benachbarten Stereozentren in hohen Ausbeuten.