Chemoenzymatic Diazo Synthesis Enabled by Enzymatic Halide Recycling with Vanadium-Dependent Haloperoxidases

Diazo compounds are privileged carbene precursors in synthetic organic chemistry. Despite their versatility in both chemo- and biocatalytic chemical synthesis, their preparation typically requires the use of reagents that are expensive, toxic, and unsustainable. Herein, we describe a chemoenzymatic strategy for the preparation of stabilized diazo compounds enabled by enzymatic halide recycling with vanadium-dependent haloperoxidase (VHPO) enzymes. The process involves the conversion of a carbonyl-containing compound to an intermediate hydrazone that is subjected directly to a VHPO-catalyzed nitrogen-nitrogen (N-N) bond oxidation to afford the corresponding diazo compound. The protocol is applied to a broad range of carbonyls with moderate to high yield and excellent chemoselectivity. A series of molecular docking, molecular dynamics, microscale thermophoresis, and mutagenesis experiments provide insight into reactivity rate differences between (E)- and (Z)-configured hydrazones in the VHPO-mediated oxidation process. Finally, the developed method is interfaced with lipase-mediated transacylation to produce a collection of diazo derivatives starting from a single benzoylformate starting material.