Photocatalytic Boryl Radicals Triggered Sequential BDN/CDN Bond Formation to Assemble Boron-Handled Pyrazoles

Vinyldiazo compounds are one of the most important synthons in the construction of a cyclic ring. Most photochemical transformations of vinyldiazo compounds are mainly focusing on utilization of their CC bond site, while reactions taking place at terminal nitrogen atom are largely unexplored. Herein, a photocatalytic cascade radical cyclization of LBRs with vinyldiazo reagents through sequential BN/CN bond formation is described. The reaction starts with the addition of LBRs (Lewis base-boryl radicals) at diazo site, followed by intramolecular radical cyclization to access a wide range of important boron-handled pyrazoles in good to excellent yields. Control experiments, together with detailed mechanism studies well explain the observed reactivity. Further studies demonstrate the utility of this approach for applications in pharmaceutical and agrochemical research. A mild strategy for the synthesis of boron-handled pyrazoles through photocatalytic cascade radical cyclization of LBRs (Lewis base-boryl radicals) with vinyldiazo reagents is described here. The reaction starts with the addition of LBRs at diazo site, followed by intramolecular radical cyclization to access a wide range of important boron-handled pyrazoles in good to excellent yields. Control experiments, together with detailed mechanism studies well explain the observed reactivity.image