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Organocatalytic Asymmetric Synthesis of 3‑Chlorooxindoles Bearing Adjacent Quaternary–Tertiary Centers

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posted on 20.02.2016, 11:06 authored by Artur Noole, Ivar Järving, Franz Werner, Margus Lopp, Andrei Malkov, Tõnis Kanger
A new methodology was developed for the synthesis of enantiomerically enriched 3,3-disubstituted 3-chlorooxindoles 3 via a Michael addition of 3-chloroxindoles to nitroolefins 2, catalyzed by chiral squaramide 10. Products with adjacent quaternary–tertiary centers were isolated in excellent yields (up to 99%), high diastereoselectivities (up to 11:1), and enantiomeric purities (up to 92%). This is the first example where 3-chloroxoindoles 1 have been used as nucleophiles in a highly stereoselective organocatalytic reaction.