Anything between ureas? Spiro[isoxazolidine-3,3′-oxindole]s have been constructed by employing methyleneindolinones and nitrones as the starting materials through [3+2] annulation catalyzed by a bisthiourea. Products with three contiguous stereocenters, including one spiroquaternary stereocenter, are obtained in good yields with excellent enantio- and diastereoselectivity. The bisthiourea catalyst acts as a multiple-hydrogen-bond donor to simultaneously activate both substrates.
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