Palladium‐Catalyzed Inverse and Normal Dehydrogenative Aza‐Morita−Baylis−Hillman Reactions with γ,δ‐Unsaturated Compounds
σ-Lewis base-catalyzed regio- and enantioselective aza-Morita−Baylis−Hillman (MBH) reaction of α,β,γ,δ-unsaturated systems remains a challenge due to the intrinsic covalent activation mode. Here we demonstrate that a Pd0 complex can mediate the dehydrogenative reaction of γ,δ-unsaturated compounds to give corresponding electron-poor dienes, which further undergo δ-regioselective umpolung Friedel−Crafts-type addition to imines via auto-tandem Pd0-π-Lewis base catalysis. After β-H elimination of in situ formed PdII-complexes, unprecedented and chemically inverse aza-MBH-type adducts are finally furnished with fair to outstanding enantioselectivity, and a diversity of functional groups and both ketimine and aldimine acceptors can be well tolerated. Moreover, switchable α-regioselective normal aza-MBH-type reaction also can be realized by tuning catalytic conditions, whereas moderate to good enantioselectivity with low to excellent Z/E-selectivity is attained.Zum Volltext
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