Diazo Chemistry and Synthetic Applications

Diazo compounds, characterised by the presence of a diazo functional group (–N₂), serve as versatile precursors to reactive metal–carbene intermediates. These intermediates enable a broad array of bond-forming events, including cyclopropanation, X–H insertion (where X = C, N, O, S), and ylide formation. Advances in reagent design have yielded bench-stable diazo-transfer agents that facilitate the conversion of amines and carbonyl compounds into diazo derivatives under mild conditions. Continuous flow techniques have emerged as a solution to the inherent safety challenges posed by gaseous or explosive diazo species, permitting in situ generation and immediate consumption of reactive intermediates. The integration of flow platforms with transition-metal catalysis has enabled telescoped sequences that bypass isolation of hazardous reagents while maintaining high selectivity and yield. These developments underpin applications spanning small-molecule drug synthesis, agrochemical manufacture and late-stage functionalisation of complex scaffolds. Growing interest in bioorthogonal and protein-modification strategies has further extended the impact of diazo chemistry to chemical biology, where reversible esterification and site-selective labelling open avenues for dynamic control of biomolecular function.

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Diazo Chemistry and Synthetic Applications publication trend

The graph below shows the total number of articles in diazo chemistry and synthetic applications across all publications each year (not limited to Nature Index journals).

Technical terms

Diazo compound: An organic molecule bearing a –N₂ group, capable of generating carbenes upon metal catalysis or thermal activation.

Diazo transfer: A reaction in which a diazo moiety is introduced into a substrate, typically via reagents such as sulfonyl azides, converting amines or carbonyls into diazo derivatives.

Carbene insertion: The process by which a metal–carbene species inserts into various X–H bonds (X = C, N, O, S), forming new C–X linkages.

Continuous flow chemistry: A technique that conducts reactions in a steady stream through narrow channels, improving heat and mass transfer, safety and scalability.

α-Diazocarbonyl compound: A diazo species in which the diazo functionality is positioned adjacent to a carbonyl group, often used in cyclopropanation and X–H insertion reactions.

References

1. Diazo compounds for the bioreversible esterification of proteins. Chemical Science (2015).
2. An Updated Synthesis of the Diazo-Transfer Reagent Imidazole-1-sulfonyl Azide Hydrogen Sulfate. The Journal of Organic Chemistry (2016).
3. Continuous synthesis and transformation of diazomethane. E3S Web of Conferences (2023).
4. Generation of Tosyl Azide in Continuous Flow Using an Azide Resin, and Telescoping with Diazo Transfer and Rhodium Acetate-Catalyzed O–H Insertion. Organic Process Research & Development (2021).
5. Exploiting Continuous Processing for Challenging Diazo Transfer and Telescoped Copper-Catalyzed Asymmetric Transformations. The Journal of Organic Chemistry (2021).