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. Polar ends: The first stereoselective organocatalyzed [3+2] cycloaddition reaction of donor‐acceptor cyclopropanes is presented. By using 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 contiguous stereocenters in high yield and stereoselectivity.