Magnetically Recoverable Ni@Cui Hybrid Nanocatalysts Affording Spiropyrroline Heterocycles From Ketoximes And Alkenes

The design of magnetic hybrid nanomaterials for cooperative activation of diverse functional groups drives future nanocatalysis toward green and sustainable multi-component organic synthesis. Here, we report the synthesis of unique Ni@CuI hybrid nanocatalysts by oxidation of the Cu-0 surface in Ni@Cu core-shell precursor using an ethanolic I-2 solution. The morphological (scanning electron microscopy and energy-dispersive X-ray spectroscopy) and structural (powder X-ray diffraction and X-ray photoelectron spectroscopy) characterizations conform the formation of Ni-0 and CuI hybrid nanocatalysts. These are efficient catalysts for the activation of oxime and olefin substrates to afford spiropyrrolines in a short time and excellent yields under green reaction conditions. The control experiments delineate the role of Cu sites as redox (I-III) triggered cleavage of N-O bond (oximes) and Ni-0 sites adsorb the olefin (C=C) which is proximity to the Cu-enamide intermediate to enhance the intermolecular cyclization lead to spiropyrrolines. The robustness of Ni@CuI hybrid nanocatalyst is demonstrated over five cycles without loss in its turnover and structural integrity, which follows ideal green chemistry metrics.