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2-Nitromethylacrylates as Useful Dinucleophiles for the Enantioselective Organocatalytic Michael/Henry Cascade Reaction
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1  Departamento de Química Orgánica II, Facultad de Ciencia y Tecnología, Universidad del País Vasco/Euskal Herriko Unibertsitatea UPV/EHU, P.O. Box 644, E-48080 Bilbao, Spain


2-Nitromethylacrylates have proved to be suitable 1,3-dinucleophiles reacting with α,β-unsaturated aldehydes in the presence of a secondary-amine catalyst to furnish Michael/Henry cascade products in moderate yields and with high enantioselectivities although with moderate diastereoselectivities. The reaction proceeds by iminium ion activation of the enal, which reacts regioselectively with the γ-carbon of the nitronate anion formed in situ, furnishing the desired cyclohexenes with three new stereocenters. Furthermore, and trying to avoid the diastereoselectivity issue, an efficient sequential Michael/Henry/dehydration reaction has been developed leading to enantiopure cyclohexadienes in moderate yields and excellent enantioselectivities.

Keywords: Michael/Henry reaction; Enantioselective cascade reaction; Iminium catalysis