Synthesis of Spiro[benzofuran-2,3′-pyrazol]-3-imines from Aurone-Derived Azadienes and Hydrazonoyl Chlorides via Regio- and Diastereospecific [2+3] Cycloaddition

Abstract An array of spiro[benzofuran-2,3′-pyrazol]-3-imines with diverse functional groups were readily assembled from aurone-derived azadienes and in-situ generated nitrilimines under mild conditions. The transformation was performed in a regio- and diastereoselective fashion, in which a synergetic [2+3] cycloaddition pathway was likely involved. This novel methodology has extended the synthetic application of aurone-derived azadienes as a kind of two-atom synthon.