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.

An asymmetric catalytic aza-Diels-Alder/ring-closing cascade reaction between acylhydrazones and in situ formed trienamines is presented. The reaction proceeds through a formal aza-Diels-Alder cycloaddition, followed by a ring-closing reaction forming the hemiaminal ring leading to chiral bicyclic azaheterocycles in moderate to good yield (up to 71 %), good enantio- (up to 92 % ee) and diastereoselectivity (up to >20:1 d.r.). Furthermore, transformations are presented to show the potential application of the formed product.

What is the most significant result of this study?This study presents an ew example of trienamine-catalyzed aza-Diels-Alder reaction providing an ew strategy for the construction of bicyclic aza-heterocycles in an enantioselective manner.

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 as tereoselective 1,3-dipolar reaction with mono-and polysubstituted nitroolefins.The reaction affords functionalizedcyclopentanes with three consecutive stereocenters in high yield and stereoselectivity.Based on the stereochemical outcome,amechanism in which the organocatalyst activates both the donor-acceptor cyclopropane and nitroolefin is proposed. Finally,c hemoselective transformations of the cycloaddition products are demonstrated.

Asymmetric Catalytic Aza-Diels-Alder/ Ring-Closing Cascade Reaction Forming Bicyclic Azaheterocycles by Trienamine CatalysisThis artwork presents the basic reaction concept of the asymmetric catalytic aza-Diels-Alder/ring-closing cascade by the operation mode of a zipper. The two molecules (red 2,4-dienal; blue hydrazone) in this reaction are mosaicked into the two chains of the zipper. The chiral slider, the diarylprolinol-silyl ether catalyst, zips together the two molecules by sliding the hand down the chains forming the bicyclic aza-heterocyclic products in a highly stereoselective manner. More information can be found in the Communication by K. A. Jørgensen et al.