[3+2] Cycloadditions of Aldiminoboranes with N -Acylpyrazoles

The [3+2] cycloaddition between aldiminoboranes and N-acylpyrazoles was successfully achieved. Aldiminoboranes, serving as C═N═B building blocks, were generated in situ via direct hydroboration of nitriles with Piers’ borane HB(C6F5)2. The [3+2] cycloaddition furnishes five-membered BN-heterocyclic compounds and notably features an acyl migration. Furthermore, the reaction exhibits a broad substrate scope with respect to both nitriles and N-acylpyrazoles, affording the target products in 56–87% isolated yields.