Perspectives on Intermolecular Azomethine Ylide [3+2] Cycloadditions with Non-Electrophilic Olefins

Abstract

Our interest in the synthesis of compact nitrogen heterocycles from abundant sources has motivated a critical analysis of the status in azomethine ylide chemistry. Despite the outstanding developments in catalytic enantioselective [3+2] cycloadditions, these are still limited to electron-poor olefins. Only a few examples can be found in the literature that report on cycloadditions using non-electrophilic alkenes and those are compiled herein. With this account we aim to extract lessons and challenges that will inspire future breakthroughs in this area. 1 Introduction 2 State-of-the-Art Using Electron-Poor Olefins 3 Research on Activated Non-Electrophilic Olefins 3.1 Aromatic Olefins 3.2 Polyenes 3.3 Hetero-Substituted Olefins 3.4 Rare Examples with Alkyl-Substituted Olefins: Norbornadiene and Tethered α-Olefins 4 Extracted Generalities 4.1 Kinetic Barrier to Non-Electrophilic Olefins 4.2 Charge Concentration: An Unsolved Thermodynamic Penalty 5 Conclusions and Outlook