Regioselectivity Change in the Organocatalytic Enantioselective (3+2) Cycloaddition with Nitrones Through Cooperative Hydrogen-Bonding Catalysis/Iminium Activation.
Fecha
2017-01-12Autor
Juste-Navarro, Veronica
Delso, Ignacio
Reyes Martín, Efraim
Tejero, Tomás
Merino, Pedro
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Chemistry. A European Journal 23 : 2764-2768 (2017)
Resumen
The reaction of nitrones with enals through iminium
activation can be modulated by using cooperative
hydrogen-bonding catalysis to induce the participation of
a nitrone ylide (C-N-C) instead of the classical C-N-O
dipole. As a consequence, N-hydroxypyrrolidines are obtained,
rather than the expected isoxazolidines. The reaction
proceeds smoothly and high enantioselectivities are
observed in all cases. By using the appropriate substrate,
polysubstituted pyrrolidines incorporating quaternary stereocenters
can be efficiently prepared.