diazoesters

Diazoesters are a class of organic compounds that contain a diazo group (−N2) bonded to an ester-bearing carbon. In most diazoesters the diazo-bearing carbon is alpha to the ester carbonyl, giving structures such as ethyl diazoacetate (EtO2C−CHN2), methyl diazoacetate (MeO2C−CHN2), and tert-butyl diazoacetate. They are widely used as precursors to metal carbenes in synthetic organic chemistry.

Synthesis and handling of diazoesters typically involve diazotransfer to activated esters or methylene derivatives using diazotransfer reagents in basic conditions. They can also be formed from other diazo precursors or through controlled transformations of α-halo esters. Diazoesters are generally unstable and can be shock- or heat-sensitive; they are usually prepared and used at low temperature and under inert or carefully controlled conditions, with attention to contaminant metals and incompatible reagents.

Reactivity and applications center on the generation of carbenes upon thermal, photochemical, or catalytic activation. The resulting carbenes insert into C–H, O–H, and N–H bonds, and add to alkenes to furnish cyclopropanes. Under transition-metal catalysis (for example, rhodium or copper catalysts), diazoesters serve as versatile carbene sources in cyclopropanation, insertion, and various multi-component reactions. The ester group tends to stabilize the resulting carbenes and steers selectivity in many transformations.

Safety and handling notes are important: diazoesters can be energetic and detonation-prone, especially when contaminated with metals or impurities. They are typically stored at low temperatures and used with appropriate protective equipment and protocols to minimize decomposition risk.