Cyclopropanation Reactions of Semi-stabilized and Non-stabilized Diazo Compounds

The cyclopropane ring is present in a large number of bio­active molecules as its incorporation often greatly alters their physiochemical properties. The synthesis of such motif is therefore of interest. Diazo compounds are versatile and powerful reagents that can be used in a broad range of reactions, including cyclopropanation processes. However, in case of unstable diazo reagents such as the donor-substituted­ variants, their inherent toxicity and instability have hampered their effective synthesis and utilization. Herein, we report the recent­ advances devoted to the safe and facile production of these potentially hazardous species and their subsequent application in cyclopropanation reactions, allowing the synthesis of more complex cyclopropylated motifs. 1 Introduction 2 Halomethylmetal-Mediated Cyclopropanations 3 Cyclopropanations through Metallic- or Free Carbenes 3.1 Transition-Metal-Catalyzed Decomposition of Diazo Compounds 3.2 Metal-Free Decomposition of Diazo Compounds 4 Michael Induced Ring Closure (MIRC) Reactions 4.1 Sulfur Ylides 4.2 1,3-Dipolar Cycloadditions 5 Conclusion