Asymmetric Synthesis\nof Optically Active Pyrazolidines\nor Pyrazoline Derivatives via Ni(II)-Bipyridine‑<i>N</i>,<i>N</i>′‑dioxide Complexes

Easily obtainable and efficient chiral <i>C</i><sub>2</sub>-symmetric bipyridine-<i>N</i>,<i>N</i>′-dioxide\nligands with Ni(OTf)<sub>2</sub> were developed for application in\ncatalyzing [3 + 2] cycloaddition reactions to synthesize optically\nactive fused pyrazolidines or pyrazoline derivatives featuring three\ncontiguous stereogenic centers by employing azomethine imines and\nα,β-unsaturated 2-acyl imidazoles, affording the corresponding\nadducts with the opposite configuration compared to previous synthetic\nproducts in 80–98% yields with 28–99% ee and >20:1\ndr.\nIn addition, subsequent amplification experiments and derivative transformations\nof the product further demonstrated the efficient catalytic performance\nof the catalyst Ni(II)-bipyridine-<i>N</i>,<i>N</i>′-dioxide complexes and the practicality of this synthesis\nmethodology.